Answer:
The correct answer is 0.91
This cannot be fit into a normal distribution. While the first 7 runners all have times relatively close, the time of the last runner is an outlier, as it is too far from the other data points. The standard deviation is calculated by taking the mean, subtracting each value from the mean, squaring the deviations, adding these, then dividing by the number of data points (7), and taking the square root. This gives an answer of SD = 0.1107.
Step 1:
Add rent & car payments
=11,250+1422
=$12,672
Step 2:
to determine %, set up a proportion
12,672 is to his total of 39,600 as x is to 100
12,672/39,600 = x/100
cross multiply
(12,672)(100) = (39,600)(x)
1,267,200= 39,600x
divide both sides by 39,600
32%= x
OR
Alternative Step 2:
12,672 ÷ 39,600= 0.32
Alternative Step 3:
0.32 x 100 = 32%
or move decimal to the right 2 places
His rent and car payments are 32% of his earnings.
Hope this helps! :)