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Mathematics

Find the mean of 25 numbers, it being given that the mean of 15 of them is 18 and the mean of remaining ones is 13.

Measures of Central Tendency

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Answer

Mean = $\dfrac{\text{Sum of terms}}{\text{Number of terms}}$

∴ Sum of terms = Mean × Number of terms

Given, mean of 15 numbers is 18

∴ Sum of 15 terms = 18 × 15 = 270

Given, mean of 10 numbers is 13

∴ Sum of 13 terms = 13 × 10 = 130

Sum of 25 terms = 130 + 270 = 400.

Mean = $\dfrac{400}{25} = 16$

Hence, the mean of 25 numbers is 16.

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