About mathematical calculation, I think we are not unfamiliar, the basic is nothing more than addition, subtraction, multiplication, division, multiplication, square root. A lot of primary and middle school students think, calculate serious point, will not be wrong, nothing to say. But if we can have some quick calculation methods, it will help us save a lot of time, which is also very beneficial for exams and daily life.
Today I'm going to focus on the calculation of a number multiplied by 11. There are three main categories.
In the first category, one digit times 11, several times 11 is tens,
Such as the six x11 = 66.
The second type, you multiply the two digits by 11, you stretch out the two digits, you leave a space in the middle, you add the two digits, you fill in the middle.
For example, 24x11 is 2 (2+4), 4 is 264. If you have to carry the digits, add the first digit. For example, 57x11 is 5 (5+7=12 to the first 5,) 7 is (5+1) 2, 7, which is 627.
The third type, the three-digit number multiplied by 11, is similar to the two-digit number multiplied by 11. The three-digit number is stretched out at both ends, leaving two Spaces in the middle, and the sum of the two adjacent numbers is filled in.
So 324x11 is 3 (3+2) (2+4) 4, so it's 3564. If a round is needed, use the same method as the second type of round. For example, 786x11 results in 7 (7+8=15 + 1 to the previous 7) (8+6=14 + 1 to the previous 5) 6, or 8646.
Further, if you have a number and you multiply it by 22,33,44, and so on, you just strip out the 11, and you can quickly figure it out. One exception to this rule is if you multiply a number by 99, an easier way to do this is to multiply one place back by 100 plus the complement of 100, for example 56x99=55x100+ (100-56) =5544. Or 56x99 is 56x (100-1) is 5600-56. But there will be abdication involved, and in general, addition is easier than subtraction, so the previous algorithm is recommended.
A very simple algorithm, learned to save a little time.
