Can you do 19 × 7 in your head? With one simple move, it takes about two seconds.
Use an easy number nearby
19 is nearly 20. So do 20 sevens: 140. But that's one seven too many, so take it away: 140 − 7 = 133.
It works because 19 sevens is just 20 sevens, minus one seven. Picture 20 rows of 7 dots with one row crossed out.
The same trick for nines
9 × 8? Ten eights is 80. Take away one eight: 72.
It works the other way too
Stuck on your three times table? 3 × 7 is two sevens, plus one more seven. 14 + 7 = 21.
Careful: add one more seven, not one. 3 × 7 isn't 14 + 1. That's the mistake most people make with this trick.
The rule
Use an easy number nearby, then add or take away one lot. (In maths lessons this is called the distributive law: 19 × 7 = 20 × 7 − 1 × 7.)
What's 19 × 6?
Show the answer
20 × 6 = 120, then take away one six: 120 − 6 = 114.
Save this for your next test
- Round to an easy number nearby.
- Multiply by the easy number.
- Add or take away one lot of the other number.
- One lot means one seven, not one.
Read the video transcript
- Can you do 19 times 7 in your head?
- Here's how to do it in two seconds.
- 19 is nearly 20. So do 20 sevens: 140.
- But that's one seven too many. Take it away: 140 minus 7 is 133.
- Because 19 sevens is just 20 sevens, minus one seven.
- Same trick for nines. 9 times 8? Ten eights is 80. Minus one eight: 72.
- And it works the other way. Stuck on your three times table?
- 3 times 7 is 2 sevens, plus one more seven.
- 14, plus 7: 21.
- Careful: add one more seven, not one.
- So here's the trick: use an easy number nearby, then add or take away one lot.
- Now you: what's 19 times 6? Tell me in the comments.
- Want maths to feel this easy? Book a free trial lesson at bloomeducationonline.com.
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