By which number should (-1/4)⁻¹ be multiplied so that the product is the…
2023
By which number should (-1/4)⁻¹ be multiplied so that the product is the reciprocal of (-7/4)⁻¹?
- A.
7/16
- B.
16/7
- C.
-16/7
- D.
-7/16
Show answer & explanation
Correct answer: A
For any non-zero rational number a, the exponent −1 gives its multiplicative inverse: a⁻¹ = 1/a. The reciprocal of any number b is the value 1/b, so that b × (1/b) = 1.
(-1/4)⁻¹ is the multiplicative inverse of -1/4, which is -4.
(-7/4)⁻¹ is the multiplicative inverse of -7/4, which is -4/7.
The reciprocal of (-7/4)⁻¹ is the reciprocal of -4/7, which is -7/4 — this is the target product.
Let x be the required number, so (-4) × x = -7/4.
Solving for x: x = (-7/4) ÷ (-4) = 7/16.
Check: (-4) × 7/16 = -28/16 = -7/4, which matches the target product, confirming the value of x.
Hence, (-1/4)⁻¹ must be multiplied by 7/16.