1. Find Combined Mean from the following data
`N_1=40,bar X_1=10`
`N_2=60,bar X_2=15`


Solution:
Combined Mean :
`bar x_12 = ( N_1 * bar (x)_1 + N_2 * bar (x)_2 )/( N_1 + N_2 )`

`bar x_12 = ( 40 * 10 + 60 * 15 )/( 40 + 60 )`

`bar x_12 = ( 400 + 900 )/(100)`

`bar x_12 = 1300/100`

`bar x_12 = 13`

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2. Find Combined Mean from the following data
`N_1=80,bar X_1=520`
`N_2=20,bar X_2=420`


Solution:
Combined Mean :
`bar x_12 = (N_1 * bar (x)_1+N_2 * bar (x)_2)/(N_1+N_2)`

`bar x_12 = (80 xx 520+20 xx 420)/(80+20)`

`bar x_12 = (41600+8400)/(100)`

`bar x_12 = 50000/100`

`bar x_12 = 500`

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3. Find Combined Mean from the following data
`N_1=20,bar X_1=50`
`N_2=50,bar X_2=12`


Solution:
Combined Mean :
`bar x_12 = (N_1 * bar (x)_1+N_2 * bar (x)_2)/(N_1+N_2)`

`bar x_12 = (20 xx 50+50 xx 12)/(20+50)`

`bar x_12 = (1000+600)/(70)`

`bar x_12 = 1600/70`

`bar x_12 = 22.8571`

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