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August 23, 2014

August 23, 2014

Posted by **anna** on Tuesday, May 7, 2013 at 6:09pm.

A small cup of coffee costs $2.

A large cup of coffee costs $3.

On Tuesday, the store sold a total of 155 cups of coffee for a total of $335.

How many small cups of coffee did the store sell on Tuesday?

- algebra -
**MathMate**, Tuesday, May 7, 2013 at 8:18pmConventional algebra:

x=number of small cups

y=number of large cups

form the system of equations

x+y=155

2x+3y=335

Solve the system for x and y.

Quick way by substituting directly:

Let 155-x=number of large cups

2x+3(155-x)=335

Solve the linear equation for x.

Faster way by mental calculations:

Assume all sold are small,

then proceeds

=2x155=310

Money left-over = $335-310 = 25

Exchange 25 small cups for 25 large cups for $25, so

small cups = 155-25=130

large cups = 25.

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