(i)\(\frac{1}{3}\times\frac{1}{4}=\frac{1\times1}{3\times 4}=\frac{1}{12}\)
\(\frac{1}{4}\times\frac{1}{3}=\frac{1\times1}{4\times3}=\frac{1}{12}\)
So,\(\frac{1}{3}\times\frac{1}{4}=\frac{1}{4}\times\frac{1}{3}\)
(ii) \(\frac{1}{2}\times\frac{1}{5}=\frac{1\times1}{2\times5}=\frac{1}{10}\)
\(\frac{1}{5}\times\frac{1}{2}=\frac{1\times1}{5\times2}=\frac{1}{10}\)
So, \(\frac{1}{2}\times\frac{1}{5}=\frac{1}{5}\times\frac{1}2{}\)

Thickness of 24 sheets = 4.32 mm
\(\therefore\) Thickness of 1 sheet = 4.32 + 24 mm
=\(\left[ \frac { 432 }{ 100 } \div 24 \right] \)mm=\(\left[ \frac { 432 }{ 100 } \times \frac { 1 }{ 24 } \right] \)
=\(\frac { 18\times 1 }{ 100\times 1 } \)mm=\(\frac { 18}{ 100} \)=0.18
Thus, the thickness of 1 sheet is 0.18 mm.

We have: 27.9 - 18.3 + 123.42 - 45.58
Making the decimals as like decimals,
27.90 - 18.30 + 123.42 - 45.58
Adding positive numbers and the negative numbers separately, we get
   27.90               18.30
+ 123.42           + 45.58
________           _______
   151.32                63.88
________            _______

2\(\frac{3}{5}\)x10  =\(\frac{13}{5}\)x10 ==\(\frac { 13\times 2 }{ 1 } \)=26

\(\frac{9}{17}\)x3 =\(\frac{9\times3}{17}\)=\(\frac{27}{17}\)or 1\(\frac{10}{17}\)

Place value of 5 in 103.2523 - Place value of 2 in 115.552
= 0.0500 - 0.002
= 0.050 - 0.002 
= \(\frac { 50 }{ 1000 } -\frac { 2 }{ 1000 } \)
= \(\frac { 50-2 }{ 1000 } =\frac { 48 }{ 1000 } \)
= 0.048

56.3\(\times\)1000= \(\frac { 563 }{ 10 } \)\(\times\)1000
= 563\(\times\)100
= 56300

We have,\(20\times \frac{4}{5}=\frac{20\times 4}{5}=\frac{80}{5}=\frac{16}{1}=16\) 
This is the required lowest form.

We have, \(2\times \frac{6}{7}=\frac{2\times 6}{7}=\frac{12}{7}\)

This is the required lowest form.
Now, dividing 12 (numerator) by 7 (denominator),
We get, quotient = 1and remainder = 5
∴ Mixed fraction =Quotient \(\frac{Reminder}{Divisor}=1 \frac{5}{7}\)

We have, \(4\times \frac{1}{3}\)=\( \frac{4\times1}{3}=\frac{4}{3}\)

This is the required lowest form,
Now, dividing 4 (numerator) by 3
(denominator), we get, quotient = 1and remainder = 1
∴ Mixed fraction =Quotient \(\frac{Reminder}{Divisor}=1 \frac{1}{3}\)

\(1\frac{4}{9}\times 6=8\frac{2}{3}\)

We have, \(5\times 2\frac{3}{7}=5\times \frac{2\times 7+3}{7}=5\times \frac{14+3}{7}\)
=\(5\times \frac{17}{7}=\frac{5\times 17}{7}=\frac{85}{7}=12\frac{1}{7}\)

\(\frac{13}{11}\times 6=\frac{13\times 6}{11}=\frac{78}{11}=7\frac{1}{11}\)

\(\frac{4}{7}\times 3=\frac{4}{7}\times \frac{3}{1}=\frac{4\times 3}{7\times 1}=\frac{12}{7}=1\frac{5}{7}\)

\(\frac{115}{198}\)