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A sum of money under compound interest doubles itself in 4 years. In how many years will it become 16 times itself? 

 

Option: 1

12 years


Option: 2

16 years


Option: 3

8 years


Option: 4

None of these


let p be the principle amount

After 4 years, the amount is 2p.

Using the compoubd intrest formula: 2p=p(1+r)4 

Divide both sides by p:2=(1+r)4

Take the fourth root of both sides: 1+r=2 1/4

Solve for r: r=2 1/4-1 

It will take 16 years 

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Posted by

Khushi singh

A certain loan amounts, under compound interest, compounded annually earns an interest of Rs.1980 in the second year and Rs.2178 in the third year. How much interest did it earn in the first year?

Option: 1

Rs.1600


Option: 2

Rs.1800


Option: 3

 Rs.1900


Option: 4

None of these

 


1800

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Posted by

Guru G

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Find the compound interest on Rs. 5000 in 2 years at 4% per annum, the interest being compounded half yearly.

 

Option: 1

R 412.16


Option: 2

R 312.16


Option: 3

R 400.16


Option: 4

R 420.16

 


412.16

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Posted by

NARENDAR

An athlete runs 200 meters race in 24 seconds. His speed is

 

Option: 1

20 km/hr


Option: 2

24 km/hr


Option: 3

28.5 km/hr


Option: 4

30 km/hr


28.5

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Posted by

Guru G

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The distance between two stations A and B is 440 km. A train starts at 4 p.m. from A and move towards B at an average speed of 40 km/hr. Another train starts B at 5 p.m. and moves towards A at an average speed of 60 km/hr. How far from A will the two trains meet and at what time?

Option: 1

200,8 p.m.


Option: 2

300,9 p.m.


Option: 3

200,9 p.m.


Option: 4

300,8 p.m.


200,9

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Posted by

Guru G

PQ is a tunnel. A dog sits at the distance of 5/ 11 of PQ from P. The train whistle coming from any end of the tunnel would make the dog run. If a train approaches P and dog runs towards P the train would hit the dog at P. If the dog runs towards Q instead, it would hit the dog at Q. Find ratio of speed of train and dog?

 

Option: 1

5:2


Option: 2

16:5


Option: 3

11:1


Option: 4

34:3


Option 3 - 11:1

########            P____5_____¶______6_____Q

"¶" is the dog located inside the tunnel PQ and #####... is a train approaching to it. 

Case 1 - Dog decides to reach point P 

Distance covered by Dog - 5 parts and train reaches at P

Case 2 - Dog decides to run towards point Q

At the time train reaches to point P, the dog covers 5 parts in direction of Q. Now the left out part covered by dog will be 1 part towards Q .

At the time dog covers 1 part and reaches Q, train covers whole 11 parts of tunnel and reaches from P to Q. 

So, 11 part of train is eual to the 1 part covered by the dog to reach Q. 

Ratio of their speeds - Train:Dog = 11:1  

 

 

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Posted by

Vaibhavi Gupta

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 The following reaction occurs in the Blast Furnace where iron ore is reduced to iron metal : Fe2O3(s)+3 CO(g) 2 Fe(l)+3 CO2(g) Using the Le Chatelier’s principle, predict which one of the following will not disturb the equilibrium ?
Option: 1  Removal of CO
Option: 2  Removal of CO2
Option: 3 Addition of CO2
Option: 4 Addition of Fe2O3  
 

\\Fe_{2}O_{3}+3CO \leftrightharpoons 2Fe+3CO \\

According to Le Chatelier's principle change in concentration by changing the amount of reactant or product affect the equilibrium. However, the addition of solid reactant won't affect the concentration.

Therefore, addition of solid Fe2O???3 will not disturb the equilibrium. 

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Posted by

vishal kumar

The ore that contains the metal in the form of fluoride is :
Option: 1 Cryolite
Option: 2 Malachite
Option: 3 Magnetite
Option: 4 Sphalerite
 

The formula of the ores -

1) Cryolite-Na_{3}AlF_{6}

[Contains the metal in the form of fluoride]

2) Malachite-\; CuCO_{3}.Cu\left ( OH \right )_{2}

3) Magnetite-Fe_{3}O_{4}

4) Sphalerite-ZnS

 

So, option 1 is correct.

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Posted by

Ritika Jonwal

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The purest form of commercial iron is:
Option: 1 wrought iron
Option: 2 pig iron
Option: 3 scrap iron and pig iron
Option: 4 cast iron
 

The purest form of iron is wrought iron.

Therefore, Option(1) is correct.

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Posted by

Kuldeep Maurya

Among the reactions (a)  - (d), the reaction(s) that does / do not occur in the blast furnace during the extraction of iron is / are :

(a)  CaO+SiO_{2}\rightarrow CaSiO_{3} (b)  3Fe_{2}O_{3}+CO\rightarrow 2Fe_{3}O_{4}+CO_{2} (c)  FeO+SiO_{2}\rightarrow FeSiO_{3} (d)  FeO\rightarrow Fe+\frac{1}{2}O_{2}
Option: 1 (C) and (D)

Option:2  (A)

Option: 3 (A) and (D)

Option: 4 (D)
 

D

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Posted by

Guru G

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