Thursday

February 26, 2015

February 26, 2015

Posted by **m** on Wednesday, April 9, 2014 at 2:15am.

- math -
**Reiny**, Wednesday, April 9, 2014 at 6:54amnumber of dimes ---- x

number of quarters --- 21-x

by value:

10x + 25(21-x) = 405

10x + 525 - 25x = 405

-15x = -120

x = 8

so 8 dimes and 21-8 or 13 quarters

or

dimes ---- d

quarters ---q

based on numbers:

d+q = 21

based on value:

10d + 25q = 405 --- 2d + 5q = 81

double the first:

2d + 2q = 42

subtract from the 2nd to give

3q = 39

q = 13

back into the first:

d + q = 13

d = 8

I find the first method easier.

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