Problem 10 · 2011 Math Kangaroo
Medium
Arithmetic & Operations
total-then-divide
When Liza the cat is very lazy and sits around the whole day, she drinks 60 ml of milk. When she chases mice she drinks a third more milk. In the past two weeks, she has chased mice on every second day. How much milk has she drunk in the past two weeks?
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Answer: B — 980 ml
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Hint 1 of 2
First find how much she drinks on a chasing day (a third more than 60 ml).
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Hint 2 of 2
Over 14 days she chases on 7 days and is lazy on the other 7.
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Approach: combine the two kinds of days
- A lazy day is 60 ml; a chasing day is a third more: 60 + 20 = 80 ml.
- In two weeks (14 days) she chases on 7 days and is lazy on 7 days.
- Total = 7 × 80 + 7 × 60 = 560 + 420 = 980 ml.
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