Weighing the baby

Question

A mother, her baby and the family dog all stand on a scale together, and it reads 170 pounds. The mother weighs 100 pounds more than the baby and the dog together, and the dog weighs 60 per cent less than the baby.

How much does the baby weigh?

Accepted Answer

The baby weighs 25 pounds. The dog weighs 10 and the mother 135. Set up. Let the baby weigh b. The dog weighs 60 per cent less, so 0.4b. Baby and dog together weigh 1.4b, and the mother weighs 100 more than that: 1.4b + 100. The total. b + 0.4b + (1.4b + 100) = 170, so 2.8b + 100 = 170, so 2.8b = 70, giving b = 25. Check. Baby 25, dog 10, mother 1.4 × 25 + 100 = 135. Total 25 + 10 + 135 = 170. The mother's 135 is 100 more than the 35 of baby and dog together. The dog's 10 is 60 per cent less than the baby's 25. All consistent. A quicker route. Baby plus dog is x; the mother is x + 100; total …

Weighing the baby

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