9^2pi is 81pi for the total region. 6^2 is 36pi for the unshaded region. Subtract those 2 values to find the area of just the shaded region
The answer is 40. Just multiply 10x4 and you get the answer
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Unit rate is like miles per hour. If John walks 500 miles in 5 hours, the unit rate is 500/5=100 miles per hour.