The least number of complete years in which a sum of money put out at 20% compound interest will be more than doubled is:

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

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. 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: 2400

Explanation:

S.I=PNR/100

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: 1080

Explanation:

Let the sum be Rs. x. Then,

 

  C . I = x * 50 300 * 100 3 - x = 343 x 216 - x = 127 x 216 

 

? 127 x 216 = 1270 

 

x = 2160 

 

Thus, the sum is Rs. 2160

 

  S . I = R s . 2160 * 50 3 * 3 * 1 100 = R s 1080

Correct Answer: Rs. 704

Explanation:

We know that,

$$\begin{gathered} S . I . = PTR 100 \\ ? P = S . I x 100 T x R \\ And also , \\ C . I = P 1 + R 100 n - 1 \end{gathered}$$

From given data, P = Rs. 8625

Now, C.I  =  $$\begin{gathered} 8625 1 + 4 100 2 - 1 \\ = 8625 26 25 2 - 1 \\ = 8625 676 625 - 1 \\ = 8625 x 51 625 \\ C . I = Rs . 703 . 80 \end{gathered}$$

Correct Answer: 5%

Explanation:

C.I =  P 1 + r 100 t - 1

 

594.5 =  5800 1 + r 100 2 - 1

  594 . 5 5800 + 1 = 1 + r 100 2

 

r 100 = 1 . 05 - 1 = 0 . 05 = > r = 5 % .

Correct Answer: 4 years

Explanation:

P 1 + 20 100 n > 2P 

 

 

 

Now, (6/5 x 6/5 x 6/5 x 6/5) > 2.

 

 

 

So, n = 4 years.

Correct Answer: 8780.80

Explanation:

when interest is reckoned using compound interest, interest being compounded annually. The difference in the simple interest and compound interest for two years is on account of the interest paid on the first year's interest  Hence 12% of simple interest = 90 => simple interest =90/0.12 =750.

As the simple interest for a year = 750 @ 12% p.a., the principal =750/0.12 = Rs.6250.

If the principal is 6250, then the amount outstanding at the end of 3 years = 6250 + 3(simple interest on 6250) + 3 (interest on simple interest) + 1 (interest on interest on interest) = 6250 +3(750) + 3(90) + 1(10.80) = 8780.80.