Answer:
34
Step-by-step explanation:
The mean is calculated as
mean = [tex]\frac{frequency(midpoint)}{frequency}[/tex]
let x be the missing frequency, then
Total frequency × midpoint
= (16 × 2) + 7x + (20 × 12) + (10 × 17) = 32 + 7x + 240 + 170 = 442 + 7x
Total frequency = 16 + x + 20 + 10 = 46 + x, thus
[tex]\frac{242+7x}{46+x}[/tex] = 8.5 ( cross- multiply )
442 + 7x = 8.5(46 + x)
442 + 7x = 391 + 8.5x ( subtract 8.5x from both sides )
442 - 1.5x = 391 ( subtract 442 from both sides )
- 1.5x = - 51 ( divide both sides by - 1.5 )
x = 34
The missing frequency is 34
