Posted by **jennifer** on Thursday, September 25, 2008 at 9:05am.

Furnace repairs

A repairman purchased several furnace -blower motors for a total cost of $210. If is cost per motor had been $5 less, he could have purchased one additional motor. How many motors did he buy at the regular rate?

Please help

- MATH -
**Damon**, Thursday, September 25, 2008 at 9:30am
regular rate = r

discount rate = (r-5)

number bought = n

number that would have been bought = (n+1)

so

210 = r n

and

210 = (r-5)(n+1) = r n + r - 5 n -5

from the first equation r = 210/n

then the second

215 = (210/n)n +210/n -5 n

5 = 210/n -5 n

5 n = 210 -5 n^2

n^2 + n - 42 = 0

(n-8)(n+7)=0

n = 8

- sorry factored wrong -
**Damon**, Thursday, September 25, 2008 at 9:35am
sorry

(n+7)(n-6) = 0

n = 6

- MATH -
**Damon**, Thursday, September 25, 2008 at 9:36am
check

r = 210/n = 35

r-5 = 30

n+1 = 7

30 * 7 = 210 check

- MATH -
**jennifer**, Thursday, September 25, 2008 at 9:39am
thank you very much

- MATH -
**Nathen**, Wednesday, February 16, 2011 at 12:07am
HELP!!!!!I need a better explination.

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