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Monday, 20 April 2026
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Mathematics Past Questions and Answers

Topic: Identity element (simple cases only)

Jamb Mathematics Questions - Identity element (simple cases only)

Question 6:
A binary operation \(\oplus\) defined on the set of real number is such that x\(\oplus\)y = xy/6 for all x, y ∈ R. Find the inverse of 20 under this operation when the identity element is 6
  • A <sup style='font-size: smaller;'>1</sup>/<sub style='font-size: smaller;'>12</sub>
  • B <sup style='font-size: smaller;'>10</sup>/<sub style='font-size: smaller;'>3</sub>
  • C <sup style='font-size: smaller;'>1</sup>/<sub style='font-size: smaller;'>20</sub>
  • D <sup style='font-size: smaller;'>9</sup>/<sub style='font-size: smaller;'>5</sub>
View Answer & Explanation
Question 7:
A binary operation Δ is defined by aΔb = a + b + 1 for any numbers a and b. Find the inverse of the real number 7 under the operation Δ, if the identity element is -1
  • A -7
  • B -9
  • C 5
  • D 9
View Answer & Explanation
Question 8:
A binary operation on the real set of numbers excluding -1 is such that for all m, n ∈ R, mΔn = m+n+mn. Find the identity element of the operation.
  • A 1
  • B Zero
  • C -<sup style='font-size: smaller;'>1</sup>/<sub style='font-size: smaller;'>2</sub>
  • D -1
View Answer & Explanation
Question 9:
A binary operation ⊗ defined on the set of integers is such that m⊗n = m + n + mn for all integers m and n. Find the inverse of -5 under this operation, if the identity element is 0
  • A -<sup style='font-size: smaller;'>5</sup>/<sub style='font-size: smaller;'>4</sub>
  • B -<sup style='font-size: smaller;'>5</sup>/<sub style='font-size: smaller;'>6</sub>
  • C Zero
  • D 5
View Answer & Explanation
Question 10:
The binary operation on the set of real numbers is defined by m*n = \(\frac{mn}{2}\) for all m, n \(\in\) R. If the identity element is 2, find the inverse of -5
  • A \(-\frac{4}{5}\)
  • B \(-\frac{2}{5}\)
  • C 4
  • D 5
View Answer & Explanation