Sage-Tips

What surprise do you get when you multiply a three digit number by 7 then by 11 then by 13?

Hi Sherrie. When you multiply 7 x 11 x 13, you get 1 001. That’s 1000 + 1. So when you multiply a three digit number (let’s write it as “abc”) by this, then abc (1000 + 1) = abc x 1000 + abc x 1 = abc 000 + abc = abcabc.

Can you multiply 3 numbers in any order?

It doesn’t matter which order you use to multiply numbers. The answer is always the same.

What should be multiplied to 2880?

Prime factorisation of 2880 = 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 × 5. Hence, 5 should be multiply to 2880 to make it perfect square.

What is a number divisible by 7 11 and 13?

If you multiply 7 x 11 x 13 you get 1001 and if you take 1001 times any three- digit number you get a six-digit number where the original three-digit number repeats. Therefore, your original six-digit number would be divisible by 1001 or 7, 11, and 13.

How do you multiply 3 digit numbers with different numbers?

Add up the digits. Divide the 3 digit number with the digits added up. Think of 2 single digit numbers. Take any one of the number among them and double it. Add 5 with the result. Multiply the result with 5. Add the second number to the answer. Subtract the answer with 4.

How do you multiply 3 or more numbers by 11?

To multiply any 3-or-more-digit number by 11, add up the various pairs of neighboring numbers in the original number, and then stick the results between the 2 outside digits of the original number while removing the inside number (s). This is quite a mouthful, I know, so the easiest way to see how it works is with an example.

What is a 3 digit number?

Lets say that the 3 digit number is a b c ¯ where a, b and c represent digits of the number. So every number e.g. 235235 or 549549 or 602602 etc., is always 235 ⋅ 7 ⋅ 11 ⋅ 13 or 549 ⋅ 7 ⋅ 11 ⋅ 13 or 602 ⋅ 7 ⋅ 11 ⋅ 13 etc. Lets say that the 3 digit number is a b c ¯ where a, b and c represent digits of the number.

How to multiply two-digit numbers by 11 in your head?

This is a quick way to multiply two-digit numbers by 11 in your head. Separate the two digits in your mind. Add the two digits together. Place the number from Step 2 between the two digits. If the number from Step 2 is greater than 9, put the ones digit in the space and carry the tens digit.

https://www.youtube.com/watch?v=Gk9rpKGYEHM