Brain Teasers
Increasing Order
The following numbers are in increasing order: 3/5 < 7/a < 9/4 < 5/b < 16/(a+b), where a and b are positive integers. What is the value of a+b?
Answer
3/5<7/a implies 3a<35, or a<=11;7/a<9/4 implies 28<9a, or a>=4;
9/4<5/b implies 9b<20, or b<=2;
5/b<16/(a+b) implies 5(a+b)<16b, or 5a<11b.
We see that a is at least 4, but b can be only 1 or 2. Since 5a<11b, a=4 and b=2, whose sum is 6.
Hide Answer Show Answer
What Next?
View a Similar Brain Teaser...
If you become a registered user you can vote on this brain teaser, keep track of which ones you have seen, and even make your own.
Solve a Puzzle
Comments hidden to avoid spoilers.
Follow Braingle!