5. A sum lent out at simple interest becomes 4480 in 3 years and 4800 in 5 years. Find the sum and the
rate of interest.
Answers
Answer:
Principle = 4000
Rate of interest = 4 %
Step-by-step explanation:
Let the sum be "p"
and rate of interest " r"
after 3 yrs the sum = ( p × r ÷100 ×3 )+p
= (3 p r ÷ 100) +p
= 4480................given.....(1)
after 5 yrs the sum = ( p × r ÷100 ×5 )+p
= (5p r ÷ 100) +p
= 4800 ..............given ......(2)
Subtracting (1) from (2) we get
(5pr÷100) +p = 4800
- [(3or ÷ 100) +p ] = - 4480
_______________________
2pr÷100 = 320
pr = 320 ×100 ÷2
= 16,000
substituting in equation (2) we get
[ ( 5 × 16000 ÷ 100 ) + p ] = 4800
800 + p = 4800
p = 4800 -800
= 4000
again substituting this value in eq (2) we get
(5pr÷100) +p = 4800
( 5×4000×r÷100) +4000 = 4800
200r = 4800 -4000
= 800
r = 800 ÷ 200
= 4
Principle = 4000
Rate of interest = 4 %
p=4000
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