Students and Teachers Forum

1. Find the value of x in the given figure.

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2.

In the figure, AB = AC, PR⊥AC, PQ⊥AB  and BS⊥AC, prove that: BS = PR + PQ.

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3. In the adjoining figure, PQRS is a parallelogram. A line AB passes through the intersection of the diagonals PR and SQ. Prove that quadrilateral APSB = quadrilateral AQRB.

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4. What type of change cannot be called development?

Development is an activity that brings bout the positive change to the individual, community and to the nation. Any activities that do not bring about any positive changes cannot be termed as development like change in .....

5. In the given ∆ ABC, D, E, F and G are the mid-ponts of BC, AD, BE and CF respectively. Prove that ∆ ABC = 8 ∆ EFG.

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6. In the figure, A, B and C are the mid-points of PR, QA and QR respectively. D is bany point of AR. Prove that, ∆ PQR = 8 BCD.

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7. In the adjoining figure, PRST is a parallelogram and PT is the median of ∆ PQR. Prove that, ∆ PQT = ∆ STR.

1. Area of ∆PTR = Area of ∆RTS [ Since Diagonal RT bisect the parallelogram] 2. Area of ∆PQT= Area of ∆RTS[ Since median PT bisect ∆PQR] 3.  Area of ∆PQT = Area of ∆RTS [ From 1 and .....

8. Write a paragraph describing your religious and social customs.

People of diverse religion and belief are the dominant features of Nepali society. People have a sense of unity, though living in the diversity. Mostly, Brahmins and Chhetris are regarded as Hindu believers.   But people from the Mongoloid .....

9. A bus starts to move from rest. If it's velocity becomes 90 km per hour after 8 s, calculate its acceleration.

Final velocity (v) = 90km/hour                              = 90000/3600                             .....

10. Why do social customs differ from one community or region to another?

The social costumes differ from one place to another because of the following things: The social norms and values differ because of the geographical distance. The social costumes of Himalayan region is different than of Hilly and Terai. This is .....

11. The given diagram shows ammonia gas preparation in laboratory.
a. Write the balanced chemical equation of the process of the gas being produced.
b. Why the mouth of the hard glass is test-tube directed downward?
c. Ammonia gas is not collected in water, why? Write the reason with balanced chemical equation.
d. How do you find out whether the gas jar is filled with ammonia or not?

a. The balanced chemical equation of the process of the gas being prepared (i.e. ammonia) is given below:     2NH4Cl + Ca(OH)2 → 2NH3 +CaCl2 + 2H2O b. The mouth of the hard glass test tube is directed downwards .....

12. Explain with balanced chemical equations when: ammonium chloride and calcium hydroxide are mixed and heated together.

When ammonium chloride (NH4Cl) and calcium hydroxide ( Ca(OH)2 ) are heated together, ammonia (NH3) gas is produced. The balanced chemical equation is given below: 2NH4Cl + Ca(OH)2 → 2NH3 +CaCl2 + .....

13. Explain with balanced chemical equations when: carbon dioxide is passed through water under pressure.

When carbon dioxide is passed through water under pressure, it product will be Carbonic acid(H2CO3). CO2  +  .....

14. Explain with balanced chemical equations when: carbon dioxide is heated with red hot coke at 900°C.

When carbon dioxide (CO2) is heated with red hot coke at 9000 C, it produce carbon monoxide. CO2 + C → .....

15. Explain with balanced chemical equations when: calcium bicarbonate is heated.

Calcium carbonate(CaCO3) is strongly heated until it undergoes thermal decomposition to form calciumoxide(CaO) and carbon dioxide(CO2).  Thermal decomposition; CaCO3(s) → CaO(s) + .....

16. Explain with balanced chemical equations when: carbon dioxide is passed through lime water for a long time.

When carbon dioxide gas is passed through lime water for a long time,  then the white precipitate of CaCO3 which is formed initially dissolves. This is due to  formation of a soluble salt calcium hydrogen carbonate ( .....

17. Write any three uses of carbon dioxide gas.

Uses of carbondioxide are as follow. i) Plants use carbon dioxide to produce carbohydrates (sugars and starches) in the process known as photosynthesis.  ii) Carbon dioxide in solid (dry ice)  and in liquid form is .....

18. Explain with balanced chemical equations when: limestone is heated strongly.

If limestone(CaCO3) is heated strongly, it breaks down to form calcium oxide(CaO) and carbon dioxide(CO2). Calcium oxide is also called quicklime. It is yellow when hot, but white when .....

19. Explain with balanced chemical equations when: a hydrocarbon (e.g. methane) is burnt in air.

When a hydrocarbon (methane - CH4) is burnt in air or oxygen, a large amount of heat is produced along with carbon dioxide and water. A balanced chemical equation is: CH4 + 2O2 ---------->  CO2 + .....

20. Explain with balanced chemical equations when: carbon is burnt with sufficient air.

Carbon react with oxygen present in air to form carbon dioxide. C + O → .....

21. Explain the process of industrial manufacture of ammonia gas along with balanced chemical equation in detail.

The Haber's process is described in the figure .....

22. Write any three uses of ammonia gas.

Ammonia is used for i) Ammonia is also used as a refrigerant gas, ii) For purification of water supplies. iii) For the manufacture of plastics, explosives, textiles, pesticides, dyes and other .....

23. Explain why carbon dioxide gas is called an acidic gas.

It is an acidic oxide of carbon. A solution of the gas (CO2) in water is called carbonic acid(H2CO3). It is a weak acid. Carbon dioxide also reacts with alkalis like sodium hydroxide forming salts, called carbonates and .....

24. How do you prepare ammonia gas in lab?

Laboratory Preparation of Ammonia Gas Principle : Ammonia Gas is prepared in the laboratory by heating a mixture of ammonium chloride ( NH4Cl ) and calcium hydroxide or slaked lime [Ca(OH)2].   2NH4Cl+CaOH2→CaCl2+2H2O+2NH3

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25. How do you prepare carbon dioxide gas in laboratory? Summarize your explanation very briefly.

Principle : Carbondioxide gas is prepared in laboratory by the action of dilute hydrochloric acid on calcium carbonate( limestone or marble). The reaction which takes place is :   CaCO3+ 2HCL →CaCl2+ H2O+CO2 . fig: Lab preparation of .....

26. Write the ratio of ammonium chloride and calcium hydroxide during the lab preparation of ammonia.

Ammonia is usually prepared by heating a mixture ofammonium chloride and slaked lime in the ratio of 2 : 3 by .....

27. Who discovered carbon dioxide by heating magnesium carbonate?

Joseph Black  (16 April 1728 – 6 December 1799) was a Scottish physician and chemist, known for his discoveries of magnesium, latent heat, specific heat, and carbon .....

28. Explain with balanced chemical equations when: burning magnesium ribbon is inserted into a gas jar containing carbon dioxide.

When a burning magnesium ribbon is introduced in the jar containing the carbon dio-oxide,  it produces the black and white smoke. The balanced chemical reaction is shown below: Mg + CO2→ MgO + .....

29. The given diagram shows the laboratory preparation of carbon dioxide gas.
a. Write the balanced chemical equation of the gas being produced.
b. Why is the mouth of the gas jar directed upward?
c. How do you find out whether the gas jar is filled with carbon dioxide or not?
d. Collection of carbon dioxide gas is not preferred in water, why?

a.) The balanced chemical equation is :  CaCO3+ 2HCL →CaCl2+ H2O+CO2 b.) Carbon dioxide is a heavy gas. It is heavier than air so instead of going up it goes down. So the mouth of the jar is directed upward and this method of collection .....

30. Write the names of two main types of WBCs.

White blood cells (WBCs), also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. The three major types of white blood cells .....

31. By how much the price of a commodity costing Rs. 10,000 after allowing 10% discount, is less than the price of a commodity costing Rs. 8000 including 13% VAT.

Here,  For first case,  The price of commodity = Rs. 10,000 - D% of Rs. 10,000                                         = Rs. .....

32. Ritic sold two cameras for Rs. 24,000 each. On one camera, he gained 20% and on the other, he lost 20%. Find the gain or loss percentage in the whole transaction.

For first camera, Cost price ( C.P1 ) = a  Selling price ( S.P1 ) = a + 20% of a or, 24000 = a + 0.2 a or, 1.2 a = 24000 ∴ a = Rs. 20,000 For second camera, Cost price ( C.P2 ) = b Selling price ( S.P2 ) = b - 20% of .....

33. The price of an article with 15% VAT is Rs. 920. What will be the price excluding VAT?

Given, Price of the article with VAT = Rs 1356 VAT percent on the article = 13% Let the price of the article without VAT be x. Then, Price of the article with VAT = x + 13% of x 1356 = x + ( 13/100 ) * x 1356 = x + 0.13x 1.13x = 1356 x = Rs .....

34. A shopkeeper allowed 10 percent discount on his goods to make 20 percent profit. If he sold a watch for Rs.10170 with 13 percent VAT, by what percent is the discount to be increased to make only 12 percent profit.

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35. In the figure, O is the centre of the circle. If AC is the chord. If EB = EC, prove that ∡AOB = ∡AEB.


 

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36. In the figure, O is the centre of the circle and two chord s AB and PQ are equal. If C & D are mid-points of AB and PQ, prove that:∡ACD = ∡PDC

Join C, O and D, O. 1. <OCA = <ODP = 90 [ Line joining center to the mid-point of the chord is perpendicular to chord] 2. OC = OD [ Equal chords are equidistant from the center] 3. <OCD = < ODC [ In triangle ODC, OC = AD, isosceles .....

37. Through each of the points of the intersection of two circles, straight lines are drawn, cutting one circle at A and B and the other at C and D. Prove that: AB ∕∕ CD.

Join P and Q. 1. < BAP = < PRD [ Being APRB is cyclic quadrilateral] 2. < PRD + PCD = 180 [ Being opposite angles of cyclic quadrilateral PRDC] 3. <BAP + < PCD = 180 [ From 1 and 2] 4. AB // CD [ <BAP + < PCD = 180, .....

38. Two circles intersect at A and B respectively. Line PAQ passes through the point A and two points R and S are in the circumference of the circles such that PR ∕∕ QS. Then prove that the line RS passes through the point B.

Join R and B, B and S, A and B. 1. < AQS + < ABS = 180 [ Being opposite angle of cyclic quadrilateral ABSQ] 2. < RPA + < ABR = 180 [ Being opposite angle of cyclic quadrilateral APRB] 3. <RPA + <AQS = 180 [ Being .....

39. In the figure, the point of contact of two circles having centres A and B is P, prove that AQ ∥ BR.



 

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40. In the figure, AQB, DPB and APC are straight lines then prove that: ∡ADP + ∡PCB = 180⁰.

Join PQ,  1. < PCB = < PQA [ Being PQBC is cyclic quadrilateral] 2. < ADP + <PQA = 180 [ Being opposite angles cyclic quadrilateral] 3. < ADP + < PCB = 180 [ From 1 and .....

41. If AC and AD are the diameters of the circle,then prove that C, B and D are collinear.

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42. The straight line PQRS cuts two circles at P, Q, R and S which are intersecting at M and N as shown in the figure. Prove that:
∡QMS + ∡PNR = 180⁰

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43. In the given diagram, A and B are the centres of two circles which intersect at X and Y. AX and AY are produced up to P and Q of the other circle respectively. Prove that  AP = AQ.

 

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44. Samikshya converted Rs.6,00,000 into pound Sterling. After one week Nepalese rupees devaluated by 5%, find whether she has profit or loss.

Let,  1 sterling = Rs. 100 Now, Rs. 600000 = 600000 / 100 = 6000 Sterling After one week, due to dealuation of the Nepalese rupees, exchange rate becomes, 1 sterling = Rs. 100 + 5% of Rs. 100 = Rs. 105 Now, 6000 sterling = .....

45. In the figure, X and Y are the centres of two circles which intersect at A and C, XA and XC are produced up to B and D of the other circle respectively. Prove that AD = BC.


 

∠Here, ABCD is cyclic quadrilateral. ∠ XAC= ∠ ACX [ XA =XC, radii of same circle] ∠ ACX= ∠ ABD [ Cyclic quadrilateral] ∠ XAC= ∠ CDB [ Cyclic quadrilateral] Hence, ∠ABD = ∠ .....

46. From the given information in the figure, prove that AB ∕∕  EF.

Construct : Join C and D 1. < BAC = < CDE [ Being ABCD is the cyclic quadrilateral] 2. < CDE = < CFE [ Inscribe angle on the same arc CE 3. < BAC =  < CFE [ From 1 and 2] 4. AB // EF .....

47. By how much is the net selling price of a shirt marked at Rs. 1200 when VAT of 13% is levied is less that Rs. 1500?

Here,  MP = SP = Rs. 1200 [ Since no discount ] Now, SP with VAT = SP + VAT % of SP                       = Rs. 1200 + 13% ⨉ Rs. 1200           .....

48. An item was sold at a loss of 30 percent . If it had been sold for Rs. 2100 more then the profit would have been 10 percent. Find CP.

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49. Find the VAT amount on the purchase of a good worth Rs. 52,100 at 15%.

Given, Price of the good = Rs 52100 VAT percent on the good = 15% Using formula, VAT amount on the good = VAT% of price of the good = 15% of 52100 = ( 15/100 )* 52100 = Rs 7815 Hence, the VAT amount on the purchase of the good is Rs .....

50. The price of an article with 13% VAT is Rs. 1356. Find the price of the article excluding VAT.

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