Arithme-tricks😉

Hello GREATMINDS💡

So today on MATHSPEDIA A+🧠we shall discuss and focus on

Wait for it 5 Arithme-tricks😉 on multiplication of some digits

After the lesson if there is a part you don't understand feel free to comment

Fig 1.

So let's begin 

1. Multiplication of two digit number by 11

                          -1-

35 × 11

Step 1- Add both digits of the two digit number

3 + 5 = 8

Step 2- Place the result in between both digits

3_8_5 = 385

Fig 2.

-2-

78 × 11= 858

Step 1- Add both digits of the two digit number

7+8= 15

Step 2- Carry the one when the result is greater than nine

7+1=8

Step 3- Place the result in between both digits 

8_5_8=858

Fig 3.

2. Multiply by 9:

      -1-

56 ×9= 504

Step 1- Multiply the number by 10:

56× 10 =560

Step 2- Subtract the original number from step 1

560 - 56= 504

Fig 4.

3. Multiply numbers between 11 and 19

    -1-

14 ×18= 252

Step 1- Add the larger number to the rightmost digit of the other number

18 + 4=22

Step 2- Put a zero at the end of the result from step 1:

22×10= 220

Step 3- Multiply the rightmost digit of both original numbers

8 × 4=32

Step 4- Add step 2 and 3

220+32 = 252

Fig 5. 

4. Multiply 2 digit numbers ending in 1

-1-

51×31= 1581

Step 1- Multiply the leftmost digits

5×3=15

Step 2- Add the leftmost digits:

5+3=8

Step 3- Place the result from step 2 next to the result from step 1

15_8=158

Step 4- Place 1 next to the result from step 3

15_8_1= 1581

5. Multiply two digits numbers having the same tens digits and their ones digits' sum is 10:

-1-

23×27=621

Step 1- Multiply the first digit by the first digit plus 1

2(2+1)=6

Step 2- Multiply the rightmost digit (if the result is a single digit, put a zero in front of it)

3×7=21

Step 3- Place the result from step 2 next to the result from step 1

6_21=621

That's all for the day GREATMINDS💡

Join us next time for more on ARITHME-TRICKS 😉

 

  Thank you

   Have a nice day

By Emehelu Kenechukwu