Carson is refilling his tires. Each tire can hold 500 cubic inches of air. Two of the tires are completely flat and empty. One tire is 40% full and the last tire is 70% full. If Carson injects 50 cubic inches of air with each pump, how many pumps will it take him to fill all the tires? Let's be accurate as possible.
User
First, if the a full tire needs 500 cubic inches of air, then two empty tires need: 500 cubic inches / tire * 2 tires = 1000 cubic inches. Accordingly, the 40% - full tire needs 500 cubic inches * (100% - 40%). So, we find the 40% - full tire needs 500 cubic inches * (60%) = 300 cubic inches. And, the 70% - full tire needs 500 cubic inches * (100% - 70%). So, the 70% - full tire needs 500 cubic inches * (30%) = 150 cubic inches. Now add up the needs of all the tires to find the total number of cubic inches needed: 1000 cubic inches + 300 cubic inches + 150 cubic inches = 1450 cubic inches. Finally, if the pumps each hold 50 cubic inches, the total number of pumps needed is 1550 cubic inches / 50 cubic inches / pump = 29 pumps.
The answer: 29.
Assistant