Step by step
The question
Question: work out 7 × 299 in your head.
7 × 299
1 Split the number
299 is close to 300: it is 300 minus 1.
Round numbers are easy to multiply.
= 7 × (300 − 1)
2 Times each part
The 7 in front of the bracket multiplies every part inside.
7 times 300, minus 7 times 1.
= 7 × 300 − 7 × 1
This is the distributive property.
a × (b − c) = a × b − a × c
distributive property
Careful!
The 7 multiplies both parts.
Not only the 300.
Careful: not 7 × 300 − 1 ✗
3 Work it out
7 times 300 is 2100.
7 times 1 is 7.
= 2100 − 7
2100 minus 7 is 2093.
= 2093
4 Check
Let's check with the other split: 299 is 290 plus 9.
2030 plus 63 is 2093 again.
So the answer is right!
7 × 290 + 7 × 9 = 2030 + 63 = 2093
Let's look back.
First: split the number.
Then: times each part.
Then: work it out.
Last: check.
Answer
= 2093