Y is partly constant and partly varies as x. When x = 3, y = 7 and when x = 5, y = 11. Find the constants of variation.
A
2,3
B
1,2
C
3,2
D
3,4
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
Form: y = a + b x.
7 = a + 3b. - - - - - - - 1
11 = a + 5b. - - - - - - 2
Solve both equations using the elimination method
Subtract: 4 = 2b ⇒ b = 2.
put b = 2 into eqn 1
a + 6 = 7 ⇒ a = 1. Constants a = 1 (constant part), b = 2 (variation constant).
Source: WAEC / JAMB / NECO Classroom Archive (Record #74100)