Answer:
a. $180
b. $7
Step-by-step explanation:
In order to easily find the cost of x amount of pens, first find the unit price:
- The unit price is the price for 1 of something
- To find how much 1 pen is, divide 144 ÷ 12 (1 dozen = 12)
- 144 ÷ 12 = 12
- 1 pen = $12
Part A - Find the cost of 15 pens:
- Since we've just found the price of 1 pen, multiply the price by 15
- 12 × 15 = $180
- 15 pens cost $180 (outrageous!)
Part B - How many pens can be bought for $84?:
- Since we know the cost of 1 pen is $12, we can work backwards on this step
- To find the amount of pens that can be bought with $84, divide 84 ÷ 12
- 84 ÷ 12 = 7
- 7 pens can be bought
