Question
Ravi invests Rs. 2,000 on simple interest at 'a%' p.a.
for 4 years and earned an interest of Rs. 800. His friend Vinay invests Rs. 4,800 on simple interest at 30% p.a. for 'b' months and earned an interest of Rs. 3,600. Find the product of 'a' and 'b'.Solution
Simple interest = (Principal × rate × time) ÷ 100 ATQ, 800 = 2,000 × a × 4 ÷ 100 Or, 800 = 80a So, 'a' = 10 And, 3,600 = (4,800 × 30 × b) ÷ (12 × 100) ...... (since, time is in months) Or, 3,600 = 120b Or, 'b' = 30 Therefore, the required product = (a × b) = 10 × 30 = 300
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