Question

keith is participating in a 4 - day cross - country biking challenge. he biked for 78, 60, and 68 miles on the first three days. how many miles does he need to bike on the last day so that his average (mean) is 67 miles per day?

Explanation:

Step1: Calculate total miles needed

The average is 67 miles per day for 4 days. So the total miles needed is the average times the number of days.
$67\times4 = 268$

Step2: Calculate total miles biked in first 3 days

Add the miles biked in the first three - days: $78 + 60+68=206$

Step3: Calculate miles needed on last day

Subtract the total miles biked in the first three days from the total miles needed.
$268 - 206=62$

Answer:

62