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Algebra_4

Chapter 83

Problem 2

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Use the process of substitution to solve the following:

Given:
There are a total of dimes and quarters in a bag.
When added up, they amount to cents total.
How many dimes, ND and quarters, NQ, are in the bag?

These facts can be written in shorthand form as:
10ND + 25NQ = = total value in cents
and
ND + NQ = = total number of coins

(a) Evaluate: ND =

(b) Evaluate: NQ =




Example:

Use the process of elimination to solve the following:

Given:
There are a total of 5 nickels and dimes in a bag.
When added up, they amount to 40 cents total.
How many nickels, NN and dimes ND, are in the bag?

These facts can be written in shorthand form as:
(1) 5NN + 10ND = 40 = total cents
and
(2) NN + ND = 5 = total number of coins

Multiply equation (2) by -5 and add it to equation (1).

This gives:
5NN + 10ND = 40
-5NN - 5ND = -25
--------------------------------------
5ND = 15

(3) or ND = 3 = (number of dimes)

Substituting equation (3) back into equation (2) gives

NN + ND = NN + 3 = 5

(4) or NN = 2 = (number of nickels)