6th grade Q1

This is how you can solve 2 step problems involving addition and subtraction of mixed decimals.

Example:

Liam's mom gave him Php 1,000.00 to buy school supplies. He spent Php 450.25 on notebooks and Php 299.50 on a new backpack. How much money does Liam have left?

Problem recap:
Liam’s mom gave him Php $1,000.00$. He spent:

• Php $450.25$ on notebooks
• Php $299.50$ on a backpack

You need to find out how much money Liam has left.

First you need to understand the problem

This is both an addition add a subtraction problem. First you need to find the total amount he spent. Then, to find out how much money is left, you need to subtract the total amount Liam spent from the total amount he was given.

Then make a plan

• First, add up how much Liam spent on notebooks and the backpack.
• Then, subtract this total from the Php $1,000.00$ he was given.

Follow these steps to solve:

Step 1: Add the amounts spent

Add the cost of the notebooks and backpack:

Align the numbers by the decimal point:

Add column by column:

Hundredths: $5+0=5$

Tenths: $2+5=7$

Ones: $0+9=9$ Decimal point: Keep it aligned.

Tens: $5+9=14$, write down $4$, carry $1$

Hundreds: $4+2=6$, plus the $1$ carried = $7$

Liam spent a total of Php $749.75$.

Step 2: Subtract the total spent from the amount given

Subtract Php $749.75$ from Php $1,000.00$:

Align the numbers by the decimal point:

Subtract column by column:

In the hundredths place, we need to subtract 5 from 0. But 0 is too small to subtract from. The digit directly to the left in the tenths place is also 0, so you can’t borrow there either. This means we have to keep going left to find a digit that’s not 0.The first non-zero digit is 1 in the thousands place.

Borrow 1 from the thousands place, turning the 1 into a 0.The diagonal line makes sure you don't forget that you have borrowed 1 thousands and have none left. The hundreds place now gets 10. Since you still need to borrow for the tenths and hundredths, you continue:

• Borrow 1 from the 10 in the hundreds place, leaving 9 in the hundreds and adding 10 to the tens place.
• Borrow 1 from the 10 in the tens place, leaving 9 in the tens and adding 10 to the ones place.
• Borrow 1 from the 10 in the ones place, leaving 9 in the ones and adding 10 to the tenths place.
• Finally, borrow 1 from the 10 in the tenths place, leaving 9 in the tenths and making the hundredths place 10.

Now that borrowing is complete, you subtract column by column:

Hundredths Place: 10−5=5

Tenths Place: 9−7=3

Ones Place: 9−9=0

Tens Place: 9−4=5

Hundreds Place: 9−7=2

The 1 in the thousands place that you borrowed from initially left 0 in thousands place. The final answer is therefore Php 250.25.

Final answer:

Liam has Php 250.25 left.

Summary for the student:

1. Add up how much Liam spent: $450.25+299.50=749.75$.
2. Subtract the total spent from the amount given: $1,000.00-749.75=250.25$.
3. Liam has Php 250.25 left!