the ratio between upper limit and lower limit of a class is 3:2.  if the class mark is 15 , then find lower limit of the class-interval.

Dear Student,

$$\begin{gathered} Let the upper limit of the class interval be 3x and the lower limit of the class interval be 2x. \\ Class mark = \frac{Upper limit + Lower limit}{2} \\ 15 = \frac{3x+2x}{2} \\ 15\times 2 = 5x \\ 30 = 5x \\ x = \frac{30}{5} \\ x = 6 \\ Hence, Lower limit = 2x = 2\times 6 = 12 \\ and Upper limit = 3x = 3\times 6 = 18 \end{gathered}$$
 

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