JAMB 2024 Mathematics · Question 31

If B varies inversely as c13^{\frac{1}{3}} and C = 27 when B = 2, find the value of the constant of proportionality K.

Options

  1. A.3
  2. B.6
  3. C.9
  4. D.12

Answer: B. 6

Explanation written with AI and checked against the answer key

1. Analyze the question

We are given that BB varies inversely as C13C^{\frac{1}{3}}. We are provided with a pair of values (C=27C = 27 and B=2B = 2) and asked to find the constant of proportionality, kk.

2. Explain the concept

In mathematics, when a variable BB varies inversely as another variable XX, it is written as:

B∝1XorB=kXB \propto \frac{1}{X} \quad \text{or} \quad B = \frac{k}{X}

where kk is the constant of proportionality.

In this specific problem, X=C13X = C^{\frac{1}{3}}, so our equation becomes:

B=kC13B = \frac{k}{C^{\frac{1}{3}}}
3. Show the solution

Step 1: Set up the equation.

B=kC13B = \frac{k}{C^{\frac{1}{3}}}

Step 2: Substitute the given values into the equation. We are told B=2B = 2 and C=27C = 27.

2=k27132 = \frac{k}{27^{\frac{1}{3}}}

Step 3: Simplify the cube root. Recall that 271327^{\frac{1}{3}} is the same as 273\sqrt[3]{27}. Since 3×3×3=273 \times 3 \times 3 = 27, then 273=3\sqrt[3]{27} = 3. So, the equation becomes:

2=k32 = \frac{k}{3}

Step 4: Solve for kk. Multiply both sides by 3:

k=2×3k = 2 \times 3
k=6k = 6
4. Identify the answer

Comparing our result (k=6k = 6) with the given options, the correct choice is B.

5. Tip

Whenever you see a fractional exponent like x1nx^{\frac{1}{n}}, remember it is just a fancy way of writing the nthn^{th} root (xn\sqrt[n]{x}). If you are dealing with large numbers, try to express them as powers of smaller numbers (e.g., 27=3327 = 3^3) to make the calculation much easier!

AI can make mistakes. Report anything that looks wrong.

Past questions © the examination body (JAMB/WAEC/NECO). DeeepSolve is not affiliated with them. Rights holders: see /copyright.