Given data:
The given time taken by Tin to type 720 words is t=15 min.
The given expression can be wriiten as,
720 word=15 min
720 words= 15(60 sec)
720 words= 900 sec
1 word = 900/720 sec
=1.25 sec
Multiplying the above equation with 864 on both sides .
864 words= 864(1.25) sec
= 1080 sec
=1080/60 min
= 18 min.
Thus, the time taken bby Tine to type 864 words is 18 min.