Question

find the digital at unit place of cube of 5321.
a) 0
b) 9
c) 5
d)1​

Answer 1

Answer:

1-d)

It is a rule in maths that if we find cube of any digit ending with 1 has always have 1 as last digit

Answer 2

Given :  5321³

To Find :  Digit at unit Place

a) 0

b) 9

c) 5

d)1​

Solution:

0³ = 0  ends with 0

1³  = 1    ends with 1

2³ = 8    end with 8

3³ = 27  ends with 7

4³ = 64  ends with 4

5³ = 125  ends with 5

6³ = 216  ends with 6

7³ = 343  ends with 3

8³ = 512  ends with 2

9³ = 729  ends with 9

As 5321 ends with 1

Hence 5321³  ends with 1

unit place of cube of 5321 is  1

Another way

5321³

= (5320 + 1)³

using (a + b)³ = a³ + b³  + 3ab(a + b)  

a = 5320

b = 1

=  5320³ + 1³  +  3(5320)(1)(5320 + 1)

=  10³ x 532³  + 10 x 3 x  532 (5321)  + 1

= 10 x 100 x 532³ + 10 x 3 x  532 (5321) + 1

= 10 (  100 x 532³ + 3 x  532 (5321) ) + 1

= 10k + 1

Hence Digit at unit place is 1

d) 1 is correct option.

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