C. 60: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, and 60
1,000: 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 125, 200, 250, 500, 1000
Now we find the common numbers. One doesn’t count as when multiplied later on, it will not change anything.
60: 2, 4, 5, 10, 20
1,000: 2, 4, 5, 10, 20
The highest common factor is 20 because it’s, well, the highest number.
D. Do the same thing for D.
24: 1, 2, 3, 4, 6, 8, 12, 24
880: 1, 2, 4, 5, 8, 10, 11, 16, 20, 22, 40, 44, 55, 80, 88, 110, 176, 220, 440, 880
20 and 880: 2, 4, 8
8 is the Highest Common Factor.
E. Do the same thing with E.
90: 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90
1,000: 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, 125, 200, 250, 500, 1000
90 and 1000: 2, 5, 10
10 is the Highest Common Factor.
This should be easy because we just have to use substitution method. Substitute the value of x from the second equation into the x of the first equation.
-4(2y) + 11y = 15
-8y + 11y = 15
3y = 15 ; y = 5
Substitute this value of y to either the first or second equation.
x = 2(5) = 10
The ordered pair is therefore (10,5).
