We all want our early learners to have a strong number sense and understanding of place value. However, once standard vertical computational algorithms are introduced, students tend to prefer to jump straight into computing rather than rely on their own number sense.
Subtraction with regroup is one task that students would often revert to algorithms as their first preference. However, if we remember to “first check with our number sense”, we can often work out the answers without algorithms. Take for example,
722 – 9 = ?
Understanding that 9 is just 1 less than 10, students can work in the tens place value first,
722 – 10 + 1 = 712 + 1
The topic of money in 3rd grade is one opportunity to encourage students to rely on their number sense before using standard algorithms.
$8.70 – $0.90 = ?
When students have a understanding of the value of each type of coin and how to make a dollar with them, it is more tangible to see that $0.90 is just $0.10 (one dime) short of $1.00 (bill).
It is so much easier to work with
$8.70 – $1.00 + $0.10 = $7.70 + $0.10
than fumbling with a bunch of coins!
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