If the mean of the following data is 37. Then the value of X is:

xi	20	30	40	85
fi	19	X	13	24

Correct option is A

Given: 

The mean of the data is 37 

Formula used:

$$Mean = \frac{f_ix_i}{fi}$$

Solution:

$$f_ix_i= ( 20\times 19) + (30\times X) +( 40\times13) + (85 \times 24)$$ 

$$f_i = 19 + X + 13 + 24$$  

Now, 

​$$37 = \frac{380 + 30X+ 520 + 2040}{56+X}$$​​

$$37 = \frac{2940 + 30X}{56+X}$$

$$37 ( 56 + X ) = 2940 + 30X$$

$$2072 + 37X = 2940 + 30X$$

$$37X - 30X = 2940 - 2072$$

$$7X= 868$$

$$X = 124$$​

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