Six men can complete the work in 12 days.
After 2 days, the same six men can complete the remaining work in 10 days.
At the same time, 6 more men joined.
Total workers = 6 + 6 = 12 men
Let x be the number of days taken to complete the work.

This is inverse proportion
x₁y₁ = x₂y₂
6 x 10 = 12 x x
\(x=\frac{6 \times 10}{12}\)
x = 5
They will take 5 days to complete the remaining work.

Let x be the amount of diesel to cover 1650 km.

This is a direct proportion.
\(\frac{x_{1}}{y_{1}} =\frac{x_{2}}{y_{2}} \)
\(\frac{108}{594} =\frac{x}{1650} \)
\(x =\frac{108 \times 1650}{594} \)
x = 300
300 litres diesel required to cover 1650 km.

6 cans of juice costs Rs. 210
1 can of juice costs \(=Rs. \frac{210}{6}=Rs. 35 \)
4 cans of juice costs = Rs. 35 x 4 = Rs. 140.

Tamilselvan deposits Rs. 5000 for every three months.
He deposits Rs. 20000 for one year.
Let x be the no. of years he can save Rs. 1,50,000

This is a direct proportion
\(\frac{x_{1}}{\mathrm{y}_{1}} =\frac{x_{2}}{\mathrm{y}_{2}} \)
\(\frac{1}{20000} =\frac{x}{150000} \)
\(x =\frac{150000}{20000} \Rightarrow x=71 / 2 \)
He can save Rs. 1,50,000 in 71/2 years.

Valli purchases 10 pens for Rs. 180
\(\therefore\) Valli purchase 1 pen for \(Rs.\frac {180}{10} =Rs.18\)
Kamala buys 8 pens for Rs. 96
\(\therefore\) Kamala buys 1 pen for \(Rs. \frac {96}{8} =Rs.12\)
= Rs. 12
\(\therefore\) Kamala bought the pen cheaper.