In Beloy's fish ball factory, it costs 25 pesos to make 15 pieces of fishball while it costs 40 pesos to make 27 pieces. Assuming that the total cost is described by a linear function, how much does it cost to make 19 pieces of fishball?
You are given 2 ordered pairs of the form
(fishballs, cost), they are (15,25) and (27,40)
just follow the same steps you would when finding any linear function
slope = (40-25)/(27-15) = 15/12 = 5/4
cost - 25 = (5/4)(fishballs - 15)
cost = (5/4)fishballs - 75/4 + 25
cost = (5/4)fishballs + 25/4
so when fishballs = 19
cost = (5/4)(19) + 25/4 = 30 pesos
or
using interpolation
15, 25
19, c
27, 40
(c-25)/(40-25) = (19-15)/(27-15)
(c-25)/15 = 4/12 = 1/3
3c - 75 = 15
3c = 90
c = 30
How did 75/4 + 25/1 became 25/4?
75/4+ 25/1 =175/4
forgive me for my ignorance but it confuses me.