Question

Three markers and four rulers cost $30.
Two markers and three rulers costs $21.
The prices of a marker and a ruler are whole numbers in dollars

(A) What is the price of a marker?
(B) What is the price on a ruler?
(C) What is the price of five markers and four rulers?

Answer 1

Answer:

the price of a ruler = $ 3

The price of a marker = $ 6

The price of 5 markers = 6 × 5 = $30

The price of four rulers = 4 × 3 = $ 12

Step-by-step explanation:

Let the cost of one ruler be r and that of a marker be m.

From the given information, we can form two simultaneous equations as follows:

3m + 4r = 30.............1

2m + 3r = 21..............2

Solving the simultaneous equations we have:

Multiply 1 by 2 and 2 by 3 to get:

6m + 8r = 60.............3

6m + 9r = 63...............4

Subtracting 3 from 4 we get:

r = 3

Substituting in 1 we get:

3 m + 4 × 3 = 30

3m + 12 = 30

3m = 30 - 12

3m = 18

m = 6

the price of a ruler = $ 3

The price of a marker = $ 6

The price of 5 markers = 6 × 5 = $30

The price of four rulers = 4 × 3 = $ 12