Question

43. (4) Let the rate of interest be ( r % ) and amount is ( ₹ x ) According to the question.
[
begin{aligned}
therefore & & D_{2} &=xleft(frac{r}{100}right)^{2}
Rightarrow & 1290-1200 &=frac{x times r}{100 times 100} times r
Rightarrow & 90 &=frac{x times r times r}{100 times 100}
1200 &=frac{x times r times 2}{100} & 1000
end{aligned}
]
Now, from Eq. (i)
[
90=frac{60000 times r}{100 times 100} Rightarrow r=15 %
]
From Eq. (ii), ( 15 times x=60000 )
( therefore quad x=₹ 4000 )

# 43. The simple interest on a certain sum of money invested at a certain rate for 2 yr amounts to * 1200. The compound interest on the same sum of money invested at the same rate of interest for 2 yr amounts to 1290. What was the principal? RRB NTPC (Phase-1) 2016 (1) * 12000 (2) * 16000 (3) 6000 (4) * 4000

Solution