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Wednesday, 28 May 2014

Maths word problems: Hermione and Ron

There was one word problem I was having trouble doing in my head:

Ron and Hermione are practicing lifting feathers into the air with magic. Hermione can lift a feather 35 meters into the air, which is 5 times as high as Ron can lift a feather. How high can Ron lift a feather with his magic?

I thought it was:

35 x 5 = ?

But that's not what I'm trying to find out. Instead I need to do division:

35 / 5 = 7

Simple!

Multiplying 2 & 3 digit numbers with 1 digit numbers

This is a trick that I didn't know before now and I am amazed! It's just made multiplication a lot easier for me. So take the following problem:


If I were to do this in my head, I would add 110 + 110 + 110. But there's a different way to do it!
Take each column individually. First, times the far right column.


Then, times the middle column:


Finally, the third column. So, 1 x 3:

Ta da!

Can't believe I never knew this!