**Problems Type 1:**

A can finish work in X days.

B can finish work in Y days.

Both can finish in Z days = **(X*Y) / (X+Y).**

Problems Type 2:

Both A and B together can do work in T days.

A can do this work in X days.

then, B can do it in Y days =** (X*T) / (X-T)**

Problems Type 3:

A can finish work in X days.

B can finish work in Y days.

C can finish work in Z days.

Together they can do work in T days = **(X*Y*Z)/ [(X*Y)+(Y*Z)+(X*Z)]**

Problems Type 4:

A can finish work in X days.

B can finish work in Y days.

A*X = B*Y

**Y = (A*X) / B**

Problems Type 5:

A can finish work in X days.

B can finish work in Y days.

A left work after P days then B need to work Q days

Q =** [(X - P) / X ] * Y**

Problems Type 6:

M1 person can do W1 work in D1 days and H1 hours

M2 person can do W2 work in D2 days and H2 hours

**M1D1H1 = M2D2H2**