Question

(1)
A sum of money is doubled in 8 years at r %
rate of compound interest per annum. At the
same rate in how many years it will be four
times of the sum ?​

Answer 1

Answer:

Step-by-step explanation:

LET THE SUM OF MONEY BE P

AMOUNT = 2P ( AS DOUBLED )

TIME = 8 YEARS

INTEREST = 2P - P = P

RATE = P* 100 / P * 8

= 100/8

=25 /2

NOW, SECOND CASE ,

AMOUNT = 4P

PRINCIPAL = P

INTEREST = 3P

TIME = 3P * 100 / 25 /2 * P

TIME = 6 YEARS

Answer 2

Answer:

A =P (I +R/100) ^N

2P = P(I +R/100)^8. (1)

4P = P(I +R/100)^N. (2)

squaring eqn (1) BHS

4p=(I +R/100)^I6. (3)

Comparing (i) and (3) N=8x2 = 16

16 yrs