What is the sum of two consecutive odd numbers, the difference of whose…

2024

What is the sum of two consecutive odd numbers, the difference of whose squares is 56?

  1. A.

    30

  2. B.

    28

  3. C.

    34

  4. D.

    32

Attempted by 1 students.

Show answer & explanation

Correct answer: B

Concept: For any two numbers that differ by a fixed amount, the difference of their squares can be found directly from the identity a2 − b2 = (a − b)(a + b) — it equals the product of their difference and their sum. Since two consecutive odd numbers always differ by 2, this identity turns the given condition on their squared difference into a simple linear equation in one unknown.

Application:

  1. Let the smaller consecutive odd number be x; then the next is x + 2.

  2. The difference of their squares is (x + 2)2 − x2 = 4x + 4.

  3. Set 4x + 4 = 56 and solve: 4(x + 1) = 56 ⇒ x + 1 = 14 ⇒ x = 13.

  4. Thus the numbers are 13 and 15, and their sum is 13 + 15 = 28.

Verification: 152 − 132 = 225 − 169 = 56, so the solution is consistent.

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