The cost of running a barbershop is partly constant and inversely proportional to the number (n) of people who come to the shop. If the cost per head for 40 people is K2400 and for 50 people is K2000. Find the cost per head for 100 people.

Step 1: Let $n$ be the number of people on the ship per day (in people).
The total cost equation is:
$17000\,Rs + 50\,\frac{Rs}{person} \times n\,people = 68000\,Rs$

Step 2: Subtract the fixed cost from both sides:
$50\,\frac{Rs}{person} \times n\,people = 68000\,Rs - 17000\,Rs$
$50\,\frac{Rs}{person} \times n\,people = 51000\,Rs$

Step 3: Divide both sides by $50\,\frac{Rs}{person}$:
$n\,people = \frac{51000\,Rs}{50\,\frac{Rs}{person}}$
$n = \frac{51000}{50}$
$n = 1020\,people$

**1020}