He bikes for 59 , 52 , and 53 miles on the first three days. How many miles does he need to bike on the last day so that his average (mean) is 56 miles

Question

Ivan is participating in a 4 -day cross-country biking challenge. He bikes for 59 , 52 , and 53 miles on the first three days. How many miles does he need to bike on the last day so that his average (mean) is 56 miles per day?

Answer 1

Phil, I see many students have a problem solving this type of problem. How do we find the average? We add the four distances and divide by 4, right? We're just missing one, but we're given the average. Let's let x = d equal the fourth days distance and plug everything in.

 

56 = (59 + 52 + 53 + d)/4

56 = (164 + d)/4

 

Since the right side is divided by 4, we multiply both sides by 4.

 

224 = 164 + d

    d = 60

 

On the last day, he must travel 60 miles to keep up his average.

 

Hope this helps!