You have two sand timers with u. One can measure 7 minutes and other can measure 11 minutes. This means that it takes 7 minutes for the sand timer to completely empty the sand from one portion to the other.
You have to measure 15 minutes using both the timers. How will u measure it??
Notice that 15 = 7 + 4 + 4 = 7 + (11-7) + (7-3)
1) Once 7 minutes timer is over reverse it. --- 7 min
11 minutes timer shall have sand meant for 4 minutes
2) Once 11 minutes timer is over reverse 7 minutes timer --- 4 min
Now 7 minutes timer shall have sand meant for 4 min
3) Once 7 minutes timer is over again it is 15 min --- 4 min
No comments:
Post a Comment