WAEC Mathematics 2014 Theory — Question 13
Question 13 of 23 from the West African Examinations Council (WAEC) Mathematics 2014 Theory paper, with the correct answer and a full explanation.
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8(a). Copy and complete the following table for multiplication modulo 11 (values: 1, 5, 9, 10). Use the table to: (i) evaluate (9⊗5)⊗(10⊗10); (ii) find the truth set of I. 10⊗m=2 II. n⊗n=4.
Model answer
Completed table (mod 11): 5⊗5=3, 5⊗9=1, 5⊗10=6, 9⊗5=1, 9⊗9=4, 9⊗10=2, 10⊗5=6, 10⊗9=2, 10⊗10=1 (i) (9⊗5)⊗(10⊗10) = 1⊗1 = 1 (ii) I. 10⊗m=2 ⟹ from the table, m=9. II. n⊗n=4 ⟹ n=9.
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