A can type 50 words in 1 min and B can type 40 words in 1 min. First A typed for 1 min then B typed for 1 min and so on. In this way typing alternately they typed 980 words. The time taken by them in typing these 980 words was:

Correct option is B

Given:

A types 50 words/min.

B types 40 words/min.

They type alternately, starting with A.

Total words typed = 980 words.

Formula Used:

​$$\text{Total time} = \left(\frac{\text{Total words}}{\text{Words per cycle}}\right) \times 2$$​​

Solution:

Work is done in cycles of 2 minutes (A types for 1 min, then B types for 1 min).

Each cycle contributes:

50+40=90 words

​$$\frac{980}{90} = 10 \text{ full cycles} + 80 \text{ extra words}$$​​

10×2=20 minutes

Remaining words = 80. Since A types first in each cycle:

A types 50 words in 1 min.

Remaining = 80 - 50 = 30 words (to be typed by B).

B types 40 words in 1 min, so 30 words take $$\frac{30}{40}$$​= 0.75 min.

Total time:

20+1+0.75=21.75 minutes

21 minutes 45 seconds.