Table of Contents
What can you multiply to get 9?
1 x 9 = 9. 3 x 3 = 9. 9 x 1 = 9.
Why do numbers divisible by 9 add up to 9?
99. Since the units/ones value is zero the sum of the digits of the sum(90+9) will not remain 9. The nine does not change the number of tens but increases the number of ones by 9 . The sum of its digits will then be a multiple of 9.
What is the sum of the first 3 prime numbers?
10 = 2 + 3 + 5 (sum of the first 3 primes).
What is the sum of all 5 digit numbers formed using 1 2 3 4 and 5 exactly once?
Out of them, each 24 will have 1, 2, 3, 4 & 5 as ten thousands, thousands, hundreds, tens & unit digit. 1 + 2 + 3 + 4 + 5 = 15 so face value of each column = 15*24 = 360. Sum = 360 (10,000 + 1,000 + 100 + 10 + 1) = 39,99,960.
What add up to 9?
2 + 7 = 9, cross out 2 and 7. 2.4 + 3 = 9, cross out 4, 3 and 2. 3. There are no other groups of numbers adding up to 9.
What are the pairs of 9?
Pair factors of 9 are:
- 1 × 9 = 9.
- 3 × 3 = 9.
What number do you get after adding 2 between 1-9?
Pick a number between 1 to 9. Add 3 to it. Multiply the result with 3. Now add 3 to it once again. If it is a 2 digit number, split the digits and add them both. The number you get after adding those 2 is 9. How? 8 clever moves when you have $1,000 in the bank.
How to add 3 to a number to make 9?
Add 3 to it. Multiply the result with 3. Now add 3 to it once again. If it is a 2 digit number, split the digits and add them both. The number you get after adding those 2 is 9.
How do you add two numbers in your mind?
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 one’s digit in the space and carry the ten’s digit. Examples: 72 x 11 = 792. 57 x 11 = 5 _ 7, but 5 + 7 = 12, so put 2 in the space and add the 1 to the 5 to get 627
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.