Question

I have a stamp collection. 70% of my stamps are Canadian and 30% are international. I have 500 more Canadian stamps than international. How many stamps do I have altogether? How many Canadian and how many international?

Answer 1

Answer: N= 375, C= 875

Step-by-step explanation:  Let Canadian stamps=C

Let International stamps=N

C=875     and        N=375

 

C - 500=N,  .70(N + C) =C

Solve the following system:

{C-500 = N |     (equation 1)

0.7 (C+N) = C |     (equation 2)

Express the system in standard form:

{-N+C = 500 |     (equation 1)

0.7 N-0.3 C = 0 |     (equation 2)

Add 0.7 × (equation 1) to equation 2:

{-N+C = 500 |     (equation 1)

0 N+0.4 C = 350 |     (equation 2)

Divide equation 2 by 0.4:

{-N+C = 500 |     (equation 1)

0. N+C = 875. |     (equation 2)

Subtract equation 2 from equation 1:

{-N+0 C = -375. |     (equation 1)

0 N+C = 875. |     (equation 2)

Multiply equation 1 by -1:

{N+0 C = 375. |     (equation 1)

0 N+C = 875. |     (equation 2)

Collect results:

Answer: |  N = 375        and             C=875