Question

20-20=25-25
(4*5)-(4*5)=(5*5)-(5*5)
4(5-5)=5(5-5)
4=5
Why are we getting answer wrong?
And why can't we take (5-5) in divide to 5(5-5)?

Answer 1

or,20-20=25-25

or,4(5-5)=5(5-5)

[This would be wrong because from here 5 will be common]

So we can write,

4*5(1-1)=5*5(1-1)

or,20=20

or,2=2

or,1+1=2(proved)

Answer 2

The error in the given calculation is simplifying 4(5-5) = 5(5-5).

Given:

20 - 20 = 25 - 25  

To find:

Identify errors in the calculation  

Solution:

Here we have 20 - 20 = 25 - 25    

As we know, 20 = 4 × 5 and 25 = 5 × 5

Given numerical expression can be written as

=> (4 × 5) - (4 × 5) = (5 × 5) - (5 × 5)  

From the Distributive Property of Multiplication,  

A(B - C) = (A × B) - (A × C)  

=> 4 (5 - 5) = 5 (5 - 5)    

=> 4(0) = 5(0)

=>  0 = 0          [ ∵ Anything × 0 = 0 => 4(0) = 5(0) = 0  ]

Therefore,

The error in the given calculation is simplifying 4(5-5) = 5(5-5).

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