What was the question for this implicit rationale, and corresponding answer?
The chips cost $0.50 a bag and he buys them 5 days a week so that's .50 * 5 = $2.50 a week. If he spends $2.50 on chips a week then over 4 weeks he will spend 2.50 * 4 = $10.00 on chips.
 The answer: 10
The question: Calvin buys a pack of chips, for $0.50, from the vending machine at lunch, 5 days a week. After 4 weeks, how much money has Calvin spent on chips?