Let's learn from a few examples.
Manny has $150. He buys a saw that costs $74.45 and a set of pliers for $24.50. At the last minute, he also decides to buy a hammer for $9.80. How much money does Danny have left?
What does the problem ask us to do? 🤔
Let’s draw a picture to help us figure it out.
It looks like we need to do two things to solve this problem.
We need to add, then subtract.
First, we add the prices of all of Manny’s purchases.
$74.45 + $24.50 + $9.80 = ?
Let's find the sum using column form:
The total cost is $108.75.
Next, we subtract the total cost from the money that Simon has.
$150 – $108.75 = ?
Tip: We add two zeros after the decimal point in $150 to match the number of decimals in the other number.
Using column form, we can figure out the difference:
Manny will have $41.25 left.
Fantastic job.
Let’s solve one more problem together
A bag of pretzel sticks costs $4.75. Shelly bought 6 bags. How much does Shelly have to pay in total?
This is making us all hungry. 😋 But first, let's solve the problem.
What do we need to do?
Yes, we need to figure out the total cost of 6 bags of pretzel.
We can multiply the price of one bag six times:
$4.75 × 6 = ?
Let's use column form to find the product:
The answer is:
Shelly has to pay $28.50 in total. ✅
Excellent work.
A book store is having a holiday sale. The store will give a $5 discount for the second book bought. Jane bought 2 books. They cost $21.20 and $17.95. How much does Jane need to pay for the two books?
Let's draw a picture to show the $5 discount for the second book bought:
This is the equation for this drawing:
$17.95 - $5 = ?
We can find the difference using column form.
So, the discounted price of the second book is $12.95.
Now, how do we find the total price of the books?
Let’s draw a picture.
An equation for this diagram is below.
$21.20 + $12.95 = ?
We can find the answer with column form.
We found our answer:
Jane needs to pay $34.15 for the two books. ✅
Excellent job.
Now, ace the practice.