Theory question 107
Commercial Arithmetic(a) A man purchased 180 copies of a book at ₦250.00 each. He sold y copies at ₦300.00 each and the rest at the discount of 5 kobo in the Naira of the cost price. If he made a profit of ₦7,125.00, find the value of y.
(b) A trader bought x bags of rice at a cost, c = 24x + 103 and sold them at a price, s = 33x − x2/20. (i) Find the expression for the profit. (ii) If 20 bags of rice were sold, calculate the percentage profit.
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(a) Cost = 180 × 250 = ₦45,000; total sales = 45,000 + 7,125 = ₦52,125
Discounted price = 250 × 0.95 = ₦237.50
300y + 237.50(180 − y) = 52,125 → 42,750 + 62.5y = 52,125
y = 150
(b)(i) Profit = s − c = 9x − x2/20 − 103
(ii) x = 20: profit = 180 − 20 − 103 = 57; cost = 24(20) + 103 = 583
Percentage profit = 57/583 × 100 ≈ 9.8%
5 kobo in the naira is a 5% discount on the cost price.