Question

If the mean of the following data is 20.2, then find the value of p.

xi	10	15	20	25	30
fi	6	8	p	10	6

Answer 1

xi	fi	fixi
10	6	60
15	8	120
20	p	20p
25	10	250
30	6	180
	\(\sum\)fi = 30+p	\(\sum\) = 610+20p

∴ 20.2 (30 + p) = 610 + 20p 

∴ 606 + 20.2p = 610 + 20p 

∴ 20.2p – 20p = 610 – 606 

∴ 0.2p = 4 

∴ p = \(\frac{4}{0.2}\) = \(\frac{40}{2}\) = 20 

∴ p = 20