Arithme-tricks😉

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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 

Comments

  1. UnknownAugust 22, 2020 at 9:46 AM

    I love this

    ReplyDelete
  2. UnknownAugust 23, 2020 at 5:58 AM

    I don't understand number 3 sir
    Please explain

    ReplyDelete
    Replies
    1. Mathspedia A+🧠August 25, 2020 at 9:35 AM

      You were told according to the first step that you should add the larger number to the rightmost digit of the other number
      And the larger number there was 18 so you were told to add 18 to the rightmost digit of the other number which is 4
      And 22 was the answer we got
      You were also told to add zero at the end of the answer in which we got 220.
      We were also told to multiply the rightmost digit of both original numbers
      That is 8 × 4 which will give us 32
      The finally add step 2 and step 3
      Which is 220 plus 32
      Leaving the final answer as 252

      Delete
    2. UnknownAugust 28, 2020 at 1:18 PM

      Thank you for the clarification sir

      Delete
  3. UnknownAugust 28, 2020 at 1:18 PM

    Nice work

    ReplyDelete

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