Question

If a large factory sells its new gadgets for $5 each it can sell 1050 per month and if it sells the same gadgets for $9 it will sell 900 per month. Assuming the relationship between price and sales is linear predict the monthly sales of gadgets to the nearest whole number if the price is $12.

Answer 1

you are given 2 ordered pairs
(5 , 1050) and (9,900)
slope = (900 - 1050)/(9-5) = - 150/4 = - 75/2

N = (-75/2)C + b
using (5,1050)
1050 = (-75/2)(5) + b
1050 + 375/2 = b
b = 2475/2

N = (-75/2)C + 2475/2 or N = -37.5C + 1237.5
where N is the number sold and C is the price of each

so when C = 12
N = -37.5(12) + 1237.5 = 787.5
number sold = 788

Answer 2

788