Question

6(b) An investor invested #x in bank M at the rate of 6% simple interest per annum and #y in bank N at the rate of 8% simple interest per annum. If a total of #8,000,000.00 was invested in the two banks and the investor received a total of #2,320,000.00 as interest from the two banks after 4 years, calculate: (i) Values of x and y; (ii) Interest paid by the second bank.

Accepted Answer

x+y=8,000,000 ...(i). Interest from M: I_M=(x x 6 x 4)/100=0.24x. Interest from N: I_N=(y x 8 x 4)/100=0.32y. 0.24x+0.32y=2,320,000 ...(ii). Substituting x=8,000,000-y into (ii): 0.24(8,000,000-y)+0.32y=2,320,000 → 1,920,000-0.24y+0.32y=2,320,000 → 0.08y=400,000 → y=5,000,000. So x=3,000,000. (i) x=#3,000,000, y=#5,000,000. (ii) Interest from bank N = (5,000,000 x 8 x 4)/100 = #1,600,000.

WAEC Mathematics 2017 Theory — Question 10

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