Question

If the arithmetic mean of the following data is 7, then \( a + b = \) \[ \begin{array}{|c|c|c|c|c|} \hline x_i & 4 & 6 & 7 & 9 \\ f_i & a & 4 & b & 5 \\ \hline \end{array} \]

• A. 4
• B. 2
• C. 3
• D. cannot be determined

Hint:

When working with data and the arithmetic mean, ensure that all values are known before solving for unknowns.

Answer 1

The Correct Option is D

We are given that the arithmetic mean is 7. The formula for the arithmetic mean is: \[ \frac{\sum f_i x_i}{\sum f_i} = 7 \] However, without knowing the values for \( a \) and \( b \), we cannot determine the sum of \( a + b \). Hence, it cannot be determined.