Part 2 – Let’s beat the calculator

Hi there!

In my previous post, we have learnt how to square a two-digit number that ends in 5, just in a second.  Now, we will use a similar method when multiplying two-digit numbers with the same first digit and second digits that sum to 10.  As before, the answer begins by multiplying the first digit by the next higher digit, followed by the product of the second digits.

Here are your examples.  Let’s try

24 × 26 (Both numbers begin with 2, and the last digits sum to 4 + 6 =10).

Since

2 × 3 = 6

and

4 × 6 =24,

therefore,

24 × 26 = 624.

Now it is your turn.  Try

53 × 57.

Well, the answer begins with

5 × 6 = 30

and ends with

3 × 7 = 21.

Thus,

53 × 57 = 3021.

Always remember that to use this method, the first digits have to be the same and the last digits must sum to 10.  Practise this new skill.  Good luck!🙂

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Posted on March 1, 2009, in Info Matematik. Bookmark the permalink. Leave a comment.

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