Speed Math for Kids Achieve Their Full Potential

How did you go  with    those?  You should  have    had no  trouble doing   all of  them    in  your    head.   The answers are:

a)  2,025

b)  2,401

c)  2,021

d)  1,936

e)  2,907

f)  3,024

g)  3,468

h)  3,672

Multiplying higher numbers

There is no reason why we can’t use 200, 500 and 1,000 as reference numbers.
To multiply by 200 we multiply by 2 and 100. To multiply by 500 we multiply by 1,000 and halve the
answer. To multiply by 1,000 we simply write three zeros after the number.
Let’s try some examples.
212 × 212 =
We use 200 as a reference number.

Both numbers are above the reference number so we draw the circles above the numbers. How much
above? Twelve and 12, so we write 12 in each circle.
They are plus numbers so we add crossways.
212 + 12 = 224
We multiply 224 by 2 and by 100.
224 × 2 = 448
448 × 100 = 44,800
Now multiply the numbers in the circles.
12 × 12 = 144
(You must know 12 times 12. If you don’t, you simply calculate the answer using 10 as a reference
number.)

Let’s   try another.    How about   multiplying 511 by  503?    We  use 500 as  a   reference   number.

Add crossways.

511 +   3   =   514