Question

# Diana’s father gave $12.90 as pocket money for a week. She spent $7.30 for buying snacks. Amount left with Diana is _____________

- $5.60
- $5.70
- $5.80
- $5.90

Hint:

###
An addition mental math technique is to dissect an addend. This approach might be more effective for some students than left-to-right addition. This method involves dividing up one addend in an equation into more manageable bits. There are certain properties that can be used while calculating which make it easy to add. Here we have given that Diana’s father gave $12.90 as pocket money for a week. She spent $7.30 on buying snacks. We have to find the amount left with Diana.

So we will break the number in an appropriate way and then show the sum.

An addition mental math technique is to dissect an addend. This approach might be more effective for some students than left-to-right addition. This method involves dividing up one addend in an equation into more manageable bits. There are certain properties that can be used while calculating which make it easy to add. Here we have given that Diana’s father gave $12.90 as pocket money for a week. She spent $7.30 on buying snacks. We have to find the amount left with Diana.

So we will break the number in an appropriate way and then show the sum.

## The correct answer is: $5.70

### Now as we know that here we have to find the step by breaking one number. The fact that there are no steps to memorise is one of the best things about mental math. The "friendly number" addition approach facilitates working with large numbers. This is due to the fact that we are, in essence, decomposing the problem into more manageable components.

Here we will use some properties which are:

- Commutative Property of Addition: if a and b are real numbers, then a+b=b+a
- Associative Property of Addition: if a,b, and c are real numbers, then (a+b)+c=a+(b+c)

Now we have given $12.90 - $7.30, let's solve this.

Amount left will be:

$12.90 - $7.30

$13 - $7.30 = $5.70 (Round up 12.90 to the nearest whole number)

$12.90 - $7.30 = $5.80 (Compensate 0.01 by adding to $5.70)

So, the amount left with diana is $5.80.

Here the concept of Break Apart Numbers is used where a number is divided in two parts to make addition easy. The concept of friendly numbers is also used so that it becomes easy for addition or subtraction purpose. Some properties like compensation is also used to solve easily. So, the money left is $5.80.