in a school each class has 7 charts to display on a notice board. Each chart must have 9 thumb tacks to support it.
a) How many tacks are needed if three classes have to display their charts on the notice board?
b) The three classes have a total of 171 tacks. How many charts could not be placed on the board?
a) 3 * 7 * 9 = 189
b) 189 - 171 = 18
18/9 = ?
18 over 9
Hi I asked the question
To solve these questions, we need to find the total number of thumb tacks required and then work backward to get the answers.
a) To find the total number of thumb tacks needed for three classes to display their charts, we first need to find the total number of charts.
Total charts = Number of classes x Charts per class
Total charts = 3 x 7 = 21 charts
Now, we can find the total number of thumb tacks needed:
Total tacks needed = Total charts x Tacks per chart
Total tacks needed = 21 charts x 9 tacks per chart
Total tacks needed = 189 tacks
Therefore, if three classes have to display their charts on the notice board, a total of 189 thumb tacks are needed.
b) To find the number of charts that could not be placed on the board when the three classes have a total of 171 tacks, we need to work backward.
First, let's find the total number of thumb tacks needed for 21 charts:
Total tacks needed = Total charts x Tacks per chart
Total tacks needed = 21 charts x 9 tacks per chart
Total tacks needed = 189 tacks
Now, we can subtract the total number of tacks given:
Charts not placed = Total tacks needed - Total tacks given
Charts not placed = 189 tacks - 171 tacks
Charts not placed = 18 tacks
Therefore, a total of 18 charts could not be placed on the notice board.