Question

The average weight of 7 potted plants is 23 pounds. An 8th potted plant is added to the pallet,

and the average weight increases to 25 pounds. What was the weight, in pounds, of the 8th

plant?

Answer 1

The weight of the 8th plant is 39lb

Explanation:

Given:

Average Weight of 7 plants = 23lb

Average Weight of 8 plants = 25lb

Required:

Weight of the 8th plant

To solve this, the total weight of the initial 7 plants need to be calculated;

`Average = (Sum-of-weights)/(Number-of-Plants)`

Substitute 23 for Average and 7 for Number of plants

`23 = (Sum-of-weights)/(7)`

Multiply both sides by 7

`7 * 23 = (Sum-of-weights)/(7) * 7`

`161 = Sum-of-weights`

Hence, the 7 plants weigh 161

Represent the weight of the 8th plant with E

When the 8th plant is added;

The sum of the weight becomes 161 + E

And the number of plants becomes 8

The average is calculated as thus

`Average = (Sum-of-weights)/(Number-of-Plants)`

`25 = (161 + E)/(8)`

Multiply both sides by 8

`8 * 25 = (161 + E)/(8) * 8`

`200 = 161 + E`

Subtract 161 from both sides

`200 -161 = 161 - 161 + E`

`39 = E`

Reorder

`E = 39`

Hence, the weight of the 8th plant is 39lb