At a party, 20% of the people were men, 55% of the remaining people were women and the rest were children. There were 100 men. How many children were there at the party?

1. Find the total number of people at the party

$20\%$ of the people $= 100$
Total number of people $= \frac{100}{20} \times 100 = 500$

2. Find the number of remaining people

Remaining people $= 500 - 100 = 400$

3. Find the percentage of children out of the remaining people

Percentage of children among the remaining $= 100\% - 55\% = 45\%$

4. Calculate the number of children

Number of children $= \frac{45}{100} \times 400 = 180$