Question

sandra says that 4\7-1\3=3\4because all you have to do is subtract the numerators and subtract the denominators. convince sandra that she is wrong

Answer 1

The answer is
`(5)/(24)`

Explanation:

Given that Sandra says that

`(4)/(7)-(1)/(3)=(3)/(4)`

Sandra do the above calculation by subtracting the numerators and subtracting the denominators. we have to convince that Sandra is wrong.

The method of above calculation is wrong. the correction calculation is done by taking the LCM of denominators so that denomination will become same and then we will subtract the denominator.

`(4)/(7)-(1)/(3)=(12-7)/(21)=(5)/(24)`

This is the correct method.

therefore, sandra is wrong.

Answer 2

When we subtract two fraction at first we make them part of the same number,

For this we take the L.C.M. of the denominators of the fractions,

Here the denominators are 7 and 3.

Since, the L.C.M (7,3) = 21

Thus, we need to make both fraction having the denominator 21.

For this, In
`(4)/(7)` we multiply 3 on both numerator and denominator.

We get,
`(4* 3)/(7* 3)=(12)/(21)`

Similarly,
`(1* 7)/(3* 7)=(7)/(21)`

Thus,
`(4)/(7) - (1)/(3) = (12)/(21) - (7)/(21)`

`(4)/(7) - (1)/(3)= (5)/(21)`

Her mistake:

She directly subtracted the fraction without making them part of same number. This is why she was wrong.