He needs 160 5-star reviews in a role. We can write a function to solve this problem. His current total stars is 4.4*160=704. Suppose he needs x more 5-star reviews, then his total stars will be 704+5x. 160+x is the new number of reviews, and the new average will be 4.7, so 4.7*(160+x)=704+5x. The solution is 160. Besides, if you want to get the answer really fast, you can see that 4.7 is right in the middle of 4.4 and 5, so you can immediately guess that the number of new 5-star reviews should be equal to the number of current reviews.
First, find the area of the shelf if it were a full circle. the formula for the area of a circle is a=pi(r squared) a=pi (10.5 squared) a=pi x 110.25 a=3.14 x 110.25 a=346.185 now, you have to divide that area by 4 to get the area of the 1/4 circle 346.185/4=86.55
