1.

At what rate percent per annum simple interest will a sum double itself in 10 years?(a) 8% (b) 10% (c) 12% (d) 12 ½ %

Answer»

(b) 10%

Because,

Let the sum be ₹ x and the rate be r%

Then,

Amount = 2x

= P + SI = 2x

= P + [(P × R × T)/100] = 2x

= x (1 + ((r × 10)/ 100)) = 2x

= (100 + (10 × r))/100 = 2

= 10 × r = 200 – 100

= r = 100/10

= r = 10 %



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