A sum of money invested at compound interest amounts to Rs. 800 in 3 years and to Rs. 840 in 4 years. The rate of interest per annum is

Correct Answer: 6

Explanation:

Let us assume Amount be 100 Rs and we calculate in CI

 First year 60% of 100 = 60 amount (100+60) is 160

 Second year 60% of 160 = 96 amount (160+96) is 256

 Third year 60% of 256 =153.6 amount (256+153.6) is 409.6

 Here the Amount of 100 Rs is quadrapled in 3 years.

 One year contains 2 half years

 Three year has 6 half years.

 Therefore,  It takes 6 half years.

Correct Answer: 1125

Explanation:

Total amount for two years =   1000 × 1 . 5 2 = 2250

 Now , interest for third year =  2250 × 50 × 1 100 = 1125

Correct Answer: 63100

Explanation:

Let the sum be Rs. x. Then,
C.I. = x ( 1 + ( 10 /100 ))^2 - x = 21x / 100 ,
S.I. = (( x * 10 * 2) / 100) = x / 5
(C.I) - (S.I) = ((21x / 100 ) - (x / 5 )) = x / 100
( x / 100 ) = 632 * x = 63100.
Hence, the sum is Rs.63,100.

Correct Answer: 625

Explanation:

sum=Rs.x

C.I=[x(1+4/100)^2-x]=(676/625x-x)=51/625

S.I=(x*4*2)/100=2x/25

x=625

Correct Answer: 15%

Explanation:

Let the rate be R% p.a. Then,

 

1800 1 + R 100 2 - 1800 - 1800 * R * 2 100 = 405

1800 100 + R 2 10000 - 1 - 2 R 100 = 405

  1800 100 + R 2 - 10000 - 200 R 10000 = 405

?

9 5 * R 2 = 405 ? R 2 = 405 * 5 9 = 225 ? R = 15 
Rate = 15%.

Correct Answer: 2.04

Explanation:

C.I. when interest
compounded yearly=rs.[5000*(1+4/100)(1+1/2*4/100)]

= Rs. 5304.

C.I. when interest is
compounded half-yearly=rs.5000(1+2/100)^3

= Rs. 5306.04
Difference = Rs. (5306.04 - 5304) = Rs. 2.04

Correct Answer: 2400

Explanation:

S.I=PNR/100

Correct Answer: Rs. 445.95

Explanation:

We know Compound Interest = C.I. = P1+r100t - 1

Here P = 2680, r = 8 and t = 2

C.I. = 26801 + 81002-1= 268027252-12= 26802725+12725-1= 2680 5225×225

= (2680 x 52 x 2)/625

= 445.95

 

Compound Interest = Rs. 445.95

Correct Answer: Rs. 19828.80

Explanation:

Let the sum be Rs. P
P{ 1 + 8 100 2- 1 } = 2828.80

 

It is in the form of   a 2 - b 2 = a + b a - b

 

P(8/100)(2 + 8/100) = 2828.80

 

P = 2828.80 / (0.08)(2.08)

 

= 1360/0.08 = 17000

 

Principal + Interest = Rs. 19828.80

Correct Answer: Rs. 441

Explanation:

Given principal amount = Rs. 8000

Time = 3yrs

Rate = 5%

C.I for 3 yrs =  $$\begin{gathered} 8000 x 105 100 x 105 100 x 105 100 - 8000 \\ = Rs . 1261 \end{gathered}$$

 

Now, C.I for 2 yrs =  $$\begin{gathered} 8000 x 105 100 x 105 100 \\ = Rs . 820 \end{gathered}$$

 

Hence, the required difference in C.I is 1261 - 820 = Rs. 441