Question

What is unit digit in the product (3547)¹⁵³×(251)⁷²?​

Answer 1

You need the unit digit in (3547)^153*251^72.

Take first expression: (3547)^153

Step 1: Take the unit digit of base = 7:

Step 2: Check it's periodicity-:

7^1=7

7^2=49 (last digit=9)

7^3=343 (last digit=3)

7^4=> last digit=1

7^5=> last digit=7

Hence periodicity of 7=4, since after that digits repeat again.

Step 3: calculate power modulus periodicity:

pmp = 153%4=1

Step 4: answer is last digit of base to the power pmp calculated in step 3:

7^1= 7 is the last digit

Step 5: Repeat same for 2nd and other expressions.

Last digit of (251)^72 is 1. Since periodicity of 1 is 1.

Step 6: Multiply results of all expressions:

Answer= 7*1=7.

Hence last digit of the product is 7.

Answer 2

What is unit digit in the product (3547)¹⁵³×(251)⁷²?

• Unit digit of (3547)¹⁵³
• will be => 7

• Unit digit of (251)⁷²
• will be 1

And after the multiplication of unit digit we get, 7×1 = 9

So, The unit digit in the product (3547)¹⁵³×(251)⁷²?

=> Will be , '7'.