100+ Simple Interest and Compound Interest TNPSC Questions - 1

Ans: B

P = Rs. 16800, R = $$6{1}/{4}$$% = $${25}/{4}$$%, T = 9 months = $${3}/{4}$$yr.

∴ S.I. = Rs. $$(16800 × {25}/{4} × {3}/{4} × {1}/{100})$$ = 787.50.

Ans: A

S.I. for 3 years = Rs. (24412.50 – 20925) = Rs. 3487.50.

S.I. for 2 years = Rs. $$({3487.50} / {3} × 2)$$ = Rs. 2325.

∴ Principal = Rs. (20925 – 2325) = Rs. 18600.

Hence, rate = $$({100 - 2325} / {18600 × 2})$$% = 6.25%.

Ans: C

Let the sum be x.

Then, S.I. = 40% of x = $${2x}/{5}$$, Rate = 5%.

∴ Time = $$(100 × {2x}/{5} × {1}/{x× 5})$$ = 8 years.

Ans: B

Gain in 2 yrs = $$[(5000 × {25}/{4} × {2}/{100}) - ({5000 × 4 × 2}/{100})]$$

= Rs. (625 - 400) = Rs. 225.

∴ Gain in 1 year = Rs. $$({225}/{2})$$ = Rs. 112.50.

Ans: C

Rs. 10 + S.I. on Rs. 10 for 11 months

= Rs. 11 + S.I. on Rs. 1 for (1 + 2 + 3 + 4 + ……+ 10) months

⇒ Rs. 10 + S.I. on Rs. 1 for 110 months

⇒ Rs. 11 + S.I. on Rs. 1 for 55 months

⇒ S.I. on Rs. 1 for 55 months = Rs. 1.

∴ Rate = $$({100 × 12} / {1 × 55})$$% = $$21{9}/{11}$$%.