Question

1(a) Without using Mathematical tables, bles or calculators, evaluate (0.09×1.21)/(3.3×0.00025) leaving the answer in standard form (Scientific Notation)
(b) A principal of GHc5,600 was deposited for 3 years at compound interest. If the interest earned was GHc1,200.00, find, correct to 3 significant figures, the interest rate per annum.

Accepted Answer

(a) (0.09×1.21)/(3.3×0.00025) = (9×10⁻²×121×10⁻²)/(33×10⁻¹×25×10⁻⁵) = (3×11×10⁻⁴)/(33×25×10⁻⁶) = (25×10⁻⁴)/(25×10⁻⁶)... simplifying: = 1.32×10⁻⁴⁻⁽⁻⁶⁾ = 1.32×10⁻⁴⁺⁶ = 1.32×10².

(b) A = P(1+r/100)ⁿ, A = Amount = P+I = 5,600+1,200 = 6,800
6,800 = 5,600(1+r/100)³
(1+r/100)³ = 6800/5600 = 1.2143
1+r/100 = ³√1.2143 = 1.0669
r/100 = 0.0669
r = 6.69% (3 s.f.)

WAEC Mathematics 2016 Theory — Question 1

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