Question

The mean length of 7 planks of wood is 1.35m. When an extra plank of wood added, the mean length of a plank of wood increased to 1.4m. What is the length of the extra plank of wood that was added? 5/6 x 2116.8

Answer 1

Mean = Sum of observation / total number of observation

Mean = 1.35m

1.35  = Sum of length of 7 wood planks/ 7

1.35*7 = Sum of the length of 7 wood planks

9.45 = Sum of the length of 7 wood planks

Let the length of extra added wood plank = x

So,

(Sum of the length of 7 wood planks + x) / 8 = 1.4m

(9.45 + x) / 8 = 1.4

9.45 + x = 1.4 * 8

9.45 + x = 11.2

x = 11.2- 9.45

= 1.75

So,

The length of extra added wood plank = 1.75m

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Answer 2

Correct Question

The mean length of 7 planks of wood is 1.35m. When an extra plank of wood added, the mean length of 8 plank of wood increased to 1.4m. What is the length of the extra plank of wood that was added.

Answer:

The length of the extra plank of wood that was added is 1.75 m.

Step-by-step explanation:

Given:

The mean length of 7 planks of wood is 1.35m.

When an extra plank of wood added, the mean length of a plank of wood increased to 1.4m.

To Find:

The length of the extra plank of wood that was added.

Solution:

As given-the mean length of 7 planks of wood is 1.35m.

The mean length of 7 planks of wood =1.35m

$The\ mean\ length\ of\ 7\ planks\ of\ wood =\frac{ Total\ Length\ of\ 7\ planks\ of\ wood }{ Total\ nos.\ of\ planks\ of\ wood }$

                                                       $1.35=\frac{ Total\ Length\ of\ 7\ planks\ of\ wood }{ 7}$

        $Total\ length\ of\ 7\ planks\ of\ wood=1.35\times7$

                                                                $=9.45m$

As given-When an extra plank of wood added, the mean length of planks of wood increased to 1.4m.

It means  The mean length of 8 planks of wood =1.4 m.

$The\ mean\ length\ of\ 8\ planks\ of\ wood =\frac{ Total\ Length\ of\ 8\ planks\ of\ wood }{ Total\ nos.\ of\ planks\ of\ wood }$

                                                           $1.4=\frac{ Total\ Length\ of\ 8\ planks\ of\ wood }{ 8 }$

          $Total\ length\ of\ 8\ planks\ of\ wood=1.4\times8$

                                                                 $=11.2m$

The length of the extra plank of wood that was added= Total length of 8 planks of wood - Total length of 8 planks of wood

                                                                                           $=11.2- 9.45 \\= 1.75 m$

Thus,the length of the extra plank of wood that was added is 1.75m.

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