Question

The mean of the following frequency distribution is 62.8. Find the missing frequency x. Class 0-20 20-40 40-60 60-80 80-100 100-120 Frequency 5 8 x 12 7 8

Answer 1

Answer: 10

Step-by-step explanation:

• fi= 40+X
• ∑ fixi= 2640+50x
• By direct method Mean = ∑ fixi/ ∑ fi

                                     ⇒62.8= 264+50x/40+X

                                     ⇒62.8(40-x) = 2640+50x

                                     ⇒2512+62.8x = 2640+50x

                                     ⇒62.8x - 50x = 2640-2512

                                     ⇒12.8x= 128

                                    ∴ X= 10

• Hence,the missing frequency is 10.

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Answer 2

direct method

direct methof