RRB NTPC Prelims Model Paper 5 with solutions

Question : 10 of 100

Marks: +1, -0

In certain time a sum becomes 4 times at the rate of 5% per annum. At what rate of simple interest the same sum becomes 8 times in the same duration?

Solution:

(3) Case I,
Principal = Rs. x
Interest = 4x – x = Rs. 3x

∴ Time ={S.I×100}/{Principal ×Rate}

={3 x×100}/{x×5} = 60 years

Case II,
Time = 60 years
Interest = Rs. 7x

∴Rate ={Interest ×100}/{Principal ×Time}

={7x× 100}/{x×60}35/3

= 112/3% per annum

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