Difference between SI and CI

I found this Video useful and hence placing this here.. Watch it and learn. If you are unable to find the video please Click Here.

Prepare well for SBI PO.

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..