DIFFERENT WAYS TO MULTIPLYING
Activity to work in pairs Here there are 5 videos with math´s techniques to multiplying. The activity consists on following next steps:
- You have to look at your video and try to understand it.
- Make a list with the main vocabulary and its translation. (At least 10 words)
- Publish a comment with that list and a summary of your video.
- Write the dialogue that you are going to use in order to explain the trick to the class. Publish it as a comment.
- Explain the trick to the class, including an example and an exercise that every student will do.
These are the pairs, with their video:
Cristina and Sara:
ReplyDeletetrick - truco
digits - digitos
twenty-three - veintitrés
times(math) - por(x)
next number - siguiente número
equals - " es igual a"
result - "resultado de la"
square(of a number) - cuadrado de un número
the same thing - lo mismo
one more - uno más
add up to 10 - suman 10
tens - decenas
unidades - units
If we want to multiply two numbers in the tens (in the case of two figures) are equal, and the units add up to 10, we have a very easy way to do it:
Example:
43x47 = (this number is valid for 3 +7 is 10, and has the same tens: 4)
First, multiply the units, 3x7 = 21
Then, multiply the number of tens by the number next to it, in this case: 4 by 5 (which is the next) is equal to 20.
The result is 2021
Another example:
36x34 = (is valid for 6 +4 = 10, and has the same tens: 6)
First, multiply the units, 6x4 = 24
Then, multiply the number of tens by the number next to it, in this case: 3 by 4 (which follows), is 12
The result is 1224
We can also multiply numbers 3 or more numbers, but only if they have the same numbers and the only thing that varies are the units.
Example:
221x229 = (is valid for 9 +1 = 10 and the rest of the numbers are the same: 22)
First, multiply the units, 1x9 = 09
Then, multiply the number of tens by the number next to it, in this case: 22 by 23 (which is the next) is equal to 506
The result is 50609
This also helps us if we multiply two numbers the same, but the sum of its units must always give 10.
Example:
25x25 =
First, multiply the units, 5x5 = 25
Then, multiply the number of tens by the number next to it, in this case: 2 of 3 (which is the next) is equal to 6.
The result is 625
So simple, if you have questions you can ask.