Snoot and Fin use near doubles to help them add two similar numbers.
NARRATOR: Hello everyone.
What are you doing?
SNOOT: (ALIEN LANGUAGE)
NARRATOR: Playing with your stacking meebs, of course.
How many meebs in your stack, Snoot?
SNOOT: (ALIEN LANGUAGE)
NARRATOR: 18! Very impressive.
What about your stack Fin?
FIN: (ALIEN LANGUAGE)
NARRATOR: 20 meebs! Wow!
That鈥檚 even more than Snoot.
I鈥檝e got an idea.
Why not stack all your meebs together to make one super stack?
BOTH: Aha!
NARRATOR: If you add 20 to 18, how many meebs will you have altogether?
SNOOT: Er鈥 Uh鈥
NARRATOR: Don鈥檛 worry Snoot.
You鈥檝e almost got the same number of meebs, so you can work it out by doubling your 18, and then adding 2, because Fin鈥檚 got 20, 2 more than you.
2 times 18 makes 36, add 2 equals 38 meebs all together.
FIN: (ALIEN LANGUAGE)
NARRATOR: Well, if you鈥檝e got another way of doing it Fin, go ahead.
Ah, I see.
You prefer to double your 20 meebs first, and then take away 2, because Snoot鈥檚 18 meebs is 2 less than your 20.
2 times 20 makes 40, take away 2 equals鈥
38 again.
SNOOT: (ALIEN LANGUAGE)
NARRATOR: I know Snoot, it鈥檚 exactly the same as what you had before.
2 times 20 take away 2 is the same as 2 times 18 add 2.
BOTH: Aha!
NARRATOR: Right then, time to take down your stacks and make one super stack.
PLIMBLE: Plimble!
NARRATOR: Now that really is a stack!
Yours is still very good鈥
础丑鈥
Are you good at doubling numbers? This can help you add numbers that are close to each other.
The trick is to double a number that you know and then add on or take away the difference.
If you know that 10 + 10 = 20 then this can help you work out 10 + 11.
10 + 11 is the same as 10 + 10 + 1 which makes 21.
Example
9 + 12 = ?
9 and 12 are both close to 10.
10 + 10 = 20
9 is 1 less than 10, so take this away.
20 鈥 1 = 19
That leaves the 12. It is 2 more than 10 so you need to add this on.
19 + 2 = 21
You鈥檝e just worked out that 9 + 12 = 21.
Fin and Snoot add up some of their favourite snacks: space grubs and astro bugs.
Snoot and Fin rearrange numbers and make number bonds when adding moons.
Find more 1st Level resources from 91热爆 Bitesize
First Level is a stage of Scotland鈥檚 Curriculum for Excellence.
More on Numbers and number processes
Find out more by working through a topic
- count11 of 25
- count12 of 25
- count13 of 25
- count14 of 25
