Question

A certain sum of money amounts to ₹8,880 in 6 years and ₹7,920 in 4 years respectively. find the principal and rate percent .

wanted a explained answer

Answer 1

Hey friend here is your answer......

Solution :

Amount at the end of 6 years = Principal + interest for 6 years

$= P \: + {I}^{6} = 8880$

Amount at the end of 4 years = Principal + interest for 4 years

$= P + {I}^{4} = 7920$

${I}^{2} = 8880 - 7920$

$= 960$

Interest at the end of 2 years = ₹960

Interest at the end of 1st year
$= \frac{960}{2}$

$= 480$

Interest at the end of 4 years = 480 X 4

$= 1,920$

$P \: + {I}^{4} = 7920$

$P \: + 1920= 7920$

$P = 7920 - 1920$

$P = 6,000$

Principal = ₹6,000

$r \: \frac{100 \: I}{pn}$
$= \frac{100 \times 1920}{6000 \times 4}$

$r \: = 8\%$

Hope it helps you......

Answer 2

Solutions :-


Given :

Interest for 6 years = ₹ 8,880
Interest for 4 years = ₹ 7,920


Find the Interest for 2 years :-

Interest for 2 years = ₹ (8880 - 7920) = ₹ 960


Find the Interest for 4 years :-

Interest for 1 years = ₹ (960/2) = ₹ 480
Interest for 4 years = ₹ (480 × 4) = ₹ 1920


Find the principle :-

Principle = 7920 - Interest for 4 years
= ₹ (7920 - 1920)
= ₹ 6000


Find the rate percent :-

Rate = (100 × Interest for 4 years)/(principal × time) %
= (100 × 1920)/(6000 × 4) %
= 192000/24000 %
= 8 %



Hence,
Principle = ₹ 6000
Rate percent = 8 %