(3m+4b) in 1 day earn Rs.(756/7) = Rs.108 ……. (1)
(11m+13b) in 1 day earn Rs.(3008/8) = Rs.376 ….. (2)
From (1), we see that to earn Rs.1 in 1 day, there should be ((3m+4b)/(108)) persons.
Similarly, from (2), to earn Rs 1 in 1 day there should be ((11m+13b)/376) persons.
And also, ((3m+4b)/108) = ((11m+13b)/376)
Or, m(3*376-11*108) = b(108*13-4*376)
=> (m/b) = (100/60) = (5/3)
Now, from (1),
(3m+4b) in a day earn Rs.108
Or, 3m+4*(3/5)m in 1 days earn Rs.108
Or, (27m/5) in 1 days earn Rs.108
1 m in 1 day earn Rs.((108*5)/27) = Rs.20
Thus, we get that a man earns Rs.20 daily and a boy earns
Rs (20*(3/5)) = Rs.12 daily.
=> 7m+9b earn Rs.(7*20+9*12) = Rs.248 in 1 day.
=> 7m+9b earn Rs.2480 in 10 days.
Note: Since both the LHS and RHS denote the same quantity: “Number. of persons earning Rs.1 in 1 day”.
We can arrive at this step directly be using cross-multiplication-division rule. Arrange the given information as follows:
Men Boys Earning Days
3 4 * 756 ÷ 7
11 13 * 3008 ÷ 8
Now,
Men(((3*3008)/8) –((11*756)/7)) = Boys(((13*756)/7)-((4*3008)/8))
Or, m(3*376-11*108) = b(108*13-4*376)
Or,(m/b) = (5/3) |