Question

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Answer 1

ANSWER

Given that mean of data is 42

sum of frequencies (N) or ∑f=100

Class interval 0−10 10−20 20−30 30−40 40−50 50−60 60−70 70−80

Frequency: 7 , 10 , x , 13 , y , 10 , 14 , 9.

0−10 7 5 35

10−20 10 15 150

20−30 x 25 25x

30−40 13 35 455

40−50 y 45 45y

50−60 10 55 550

60−70 14 65 910

70−80 9 75 675

_________ ______

63+x+y 2775+25x+45y

Given N=100

⇒63+x+y=100

x+y=100−63=37

x+y=37

we know mean =∑=42=100=2775+25x+45y

4200=2775+25x+145y

⇒25x+45y=1425

5(5x+9y)=5×285

5x+9y=285

(1)×9=9x+9y=333

(2)=5x+9y=285

___________________

4x=48

⇒x=12

(1) ⇒x+y=37

⇒y=37−x=37+12=25

y=25.