Bob earns $4 each cookie he sells. Andres earns $3. If Andrés sold twice as many cookies as bob , how many did he sell to earn $20 more than bob?

Question

Help !!!! I cant figure thus out !!! Thanks.

Answer 1

A simple way to do this problem with no formulas is by process of elimination. For example, start with Andres selling 30 and Bob selling 20 (because Bob's number always has to be 10 less than Andres).

 

Andres 3 x 30 = $90

Bob 4 x 20 = $80

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Difference = $10

 

So this is off by 10, lets try making Andres sell 20 cookies and Bob sell 10.

 

Andres 3 x 20 = $60

Bob 4 x 10 = $40

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Difference = $20

 

There you go, you have the answer. Using the process of elimination and common sense can help in most situations when you forget a forget a formula.