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Mixing operations
Multistep calculation problems are very common in daily life.
For example, you might purchase four Tshirts at $15.00 each and six pairs of socks at $5.00 per pair. To find the total cost of the items you need to do several things.
 Decide on the calculations you need to perform and the order you will do them in.

Make strategic decisions about the best way to carry out the calculations.
In multistep problems there are often many choices of strategy.  Find ways to 'park' the information so you can manage the memory load.
In the clothing example, you need to:
 realise that the total cost of the Tshirts can be found by using 4 \(\times\) 15 = 60 and the total cost of the socks can be found by using 6 \(\times\) 5 = 30
 add these amounts to get a total cost.
This is not the only strategic choice you could make.
If you treat one Tshirt with one pair of socks as a combination you can solve the problem using 4 \(\times\) (15 + 5) + 2 \(\times\) 5 = $90.00.
Along the way to your solution you might jot down important information such as the result of each multiplication.
You can download a table of types of combined operations problems to create different problems for your students.