Time and work (method - 2)

 We solve time and work problems also by using time and efficiency. So now, we see hoe to solve in this method.

               

	A	B
Time T
Efficiency E

The table is the basic rule. Now when we fill the columns in table, Ta * Ea  = Tb * Eb

ie., efficiency should be appropriate. Here Efficiency is nothing but the ratio in reverse order.

Efficiencies should be noted in reverse order..  of ratios.

If Ratios of A and B are 2:3, then efficiencies must be.. 3:2… Now Ea=3 and Eb=2

Now,  work done is..W = T x E (of  either A or B, as both are same)

Work done by A = W/Ea                 ;(Ea=Efficiency of A)

Work done by B = W/Eb                  ; (Eb=Efficiency of B)

Work done by A+B = W/E(a+b)     ; (Ea+b=Sum of Efficiencies of A and B)

Example:

A can do a work in 10 days. B can complete the same work in 20 days. If they work together, how many days they take to complete.

Ans : 6 2/3 days

Solution:

    A   B

T  10 20                                                                                                 w = 20

E   2   1 (as Ratio of A and B but in reverse order…)            Wa+b = 20/3 = 6 2/3 days…

 Refer Method - 1 here..