Jack, who weighs 60 pounds, wants to play on the see-saw with his cousin Anna, who weighs 40 pounds. How many 4-pound rocks does Jack need to hold to make their weights equal? Give the rationale and then the answer.
Let's think step by step. First find the total difference in weight between the two people: 60 pounds - 40 pounds = 20 pounds. Then divide the weight difference by the weight of each rock to find the number of rocks need to even the weights: 20 pounds / 4 pound / rock = 5 rocks.. The answer is: 5.

In a restaurant, a burger costs $9, and a pizza twice as much. How much would cost one pizza and three burgers? Give the rationale and then the answer.
Let's think step by step. One pizza costs twice as much as the burger, which means 9 * 2 = $18. Three burgers would cost 9 * 3 = $27. So one pizza and three burgers would cost in total 18 + 27 = $45.. The answer is: 45.

A fruit and vegetable merchant installed 15 kg of carrots, 13 kg of zucchini and 8 kg of broccoli. He sold only half of them. What mass of vegetables did he sell? Give the rationale and then the answer.
Let's think step by step. You first need to know the total weight of the vegetables, so you add each quantity: 15 + 13 + 8 = 36 kg. Then you have to find half of 36: 36 / 2 = 18 kg. So, he sold 18 kg of vegetables.. The answer is: 18.