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corona
06-15-2006, 06:54 PM
I am having trouble writing an equation for this word problem using an inequality (< or >). :(

Rick's Automotive charges \$50 plus \$15 for each (15-min) unit of time when making a road call. Twin City Repair charges \$70 plus \$10 for each unit of time. Under what circumstances would it be more economical for a motorist to call Rick's?

Any suggestions?

tkhunny
06-15-2006, 07:16 PM
I am having trouble writing an equation for this word problem using an inequality (< or >). :(

Rick's Automotive charges \$50 plus \$15 for each (15-min) unit of time when making a road call. Twin City Repair charges \$70 plus \$10 for each unit of time. Under what circumstances would it be more economical for a motorist to call Rick's?

Any suggestions?Always suggestions.

U = Units of time needed
Rick = What Rick Charges = \$50 + \$15*U
Twin = What Twin Charges = \$70 + \$10*U

We're interested in using Rick, so we want to know when Twin costs more.

\$70 + \$10*U > \$50 + \$15*U

Can you finish?

corona
06-15-2006, 07:28 PM
\$70 + \$10(u) > \$50 + \$15(u)

\$20 > \$5(u)

4 > u

Which would be 1 hour.

Thank you so much for your help!

tkhunny
06-16-2006, 01:50 PM
4 > u

Which would be 1 hour.I'm a little worried about your conclusion. It's an INequality and you concluded Equality in your final statement.

What you have is u < 4, so time requirements less than one hour are what we seek. At exactly one hour, there is no difference in price. Over one hour, Rick starts getting expensive.