Answer: Choice C
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Work Shown:
- c = salary for Charles before the raise
- w = salary for William before the raise
Their salaries are in ratio 5:9 which means
c/w = 5/9
9c = 5w
w = 9c/5
w = 1.8c
Whatever Charles is earning, multiply by 1.8 to find how much William makes. This is before the raise of RM 4200.
After the raise for each person, then,
- c+4200 = new salary for Charles
- w+4200 = new salary for William
Their new salaries form the ratio 22:27, so,
(c+4200)/(w+4200) = 22/27
(c+4200)/(1.8c+4200) = 22/27
27(c+4200) = 22(1.8c+4200)
27c+113400 = 39.6c+92400
27c-39.6c = 92400-113400
-12.6c = -21000
c = -21000/(-12.6)
c = 1666.66666666667
c = 1666.67
Before the raise, Charles has a salary of RM 1666.67
Before the raise, William has a salary of w = 1.8c = 1.8*1666.67 = 3,000.006 which rounds to RM 3000.01
Add on 4200 to find William's salary after the raise.
3000.01+4200 = 7200.01
Unfortunately this isn't listed among the answer choices, but 7199.97 is fairly close. There's probably rounding error somewhere in my steps, or perhaps your professor made a rounding error. I'm not entirely sure.
In any event, it appears your teacher intends the answer is choice C.