Mathematics
WAEC 2023 Q7: One-third of a sum is 12, Twice difference is 12
BAMIDELE, KAYODE · 21 October 2026
WAEC 2023 Mathematics Question 8 Solution (Simultaneous Equation) - Step by Step
Question (WAEC 2023 Q7):
One-third of the sum of two numbers is 12, twice their difference is 12. Find the numbers.
Why students fail this:
WAEC marking scheme gives B1 for forming equations, M1 for adding, A1 for final answer. If you write only answer, you get 0.
Step 1: Notice that...
We have two unknown numbers. Let them be x and y.
First statement: one-third of sum is 12.
(1/3)(x + y) = 12 Multiply both sides by 3: x + y = 36 ... (i)
Second statement: twice their difference is 12.
2(x - y) = 12<br> Divide by 2: x - y = 6 ... (ii)
Step 2: It follows that...
We now have two simple equations: x + y = 36 x - y = 6
Add (i) and (ii): (x+y) + (x-y) = 36 + 6<br> 2x = 42 x = 21
Step 3: Hence, find y Substitute x = 21 into (i):
21 + y = 36 y = 36 - 21 = 15
Final Answer: x = 21, y = 15
Check
21+15=36, one-third is 12 correct.
21-15=6, twice is 12 correct.
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