Silly graphs (GraphJam)

Just got some good laughs reading the blogpost at SquareCircleZ about funny graphs from GraphJam. Go take a look!

(The GraphJam site itself is not always family-friendly, but the blogpost I'm linking to is fine.)

A percentage problem

Can you help me solve this question?

Jayne is given £5 for her birthday.

She spends 30% of it.

How much of her birthday money does she spend?

And... Is my method correct for this question?

100-30=70

70/5=14

1.40

No, the asker's method is not correct. In fact, it looks to me like she is randomly doing operations with numbers...

To find 30% of something, one MENTAL MATH method that I like is to first find 10% of that something.

Now, 10% of something is of course 1/10 of it. And to find 1/10 of it, just divide that by 10.

So, we divide £5 by 10 to find 1/10 of £5. It is £0.50. That's 10% of the total. And 30% of the total is three times as much, or £1.50.

So Jayne spent £1.50.

See also this video that explains how to find percentages using mental math:

Math Mammoth Light Blue Series bundles for grades 1-3 and 4-6

Now you can purchase Math Mammoth Light Blue series as a bundle for grades 1-3, or for grades 4-6, for a discounted price of $64.

Previously I've had available a bundle for all six grades (and still do), but now you can just grab either the three lower elementary or the three upper elementary grade levels with the same 33% discount.

Please see the order page here.