Question

Ram can count 100 notes of Rs 100 in 1 min.Counting machine can do it in 20 s. If they work together they will count 100 notes in
(a) 12 s (b) 14 s (c) 13 s (d) 15 s​

Answer 1

__________15 Seconds_________

Answer 2

Answer:

Time taken by Ram and Counting machine to count 100 notes = 15 sec

Step-by-step explanation:

Given data

Ram can count 100 notes of Rs 100 in 1 minute

counting machine can do it in 20 sec  

here we need to find if they work together how much time will they  take to count 100 notes

Ram can count 100 notes in 1 minute

which means in 60 sec Ram can count 100 notes

the number of notes can be counted by Ram in 1 sec

                                             = 100/60 = 10/6 = 5/3

counting machine can count 100 notes in 20 sec

number of notes can be counted by counting machine in 1 sec

                                            = 100/20 = 5 notes  

if they work together then number notes can be counted in 1 sec = 5+ 5/3

                                                                  = $\frac{15+5}{3}$ = $\frac{20}{3}$

20/3 notes can be counted in 1 sec

time taken to count 100 notes = $\frac{1}{\frac{20}{3} } (100)$  

                                                  = $\frac{3}{20} (100)$ = 3(5) = 15 sec

time taken by Ram and Counting machine to count 100 notes = 15 sec