Another great puzzle at BrainBrashers today:

A cricketer’s average in his first 20 innings was 15 runs per innings. After a further 10 innings, his average had increased to 17 runs per innings. What was his average for the last 10 innings?

How in the world is cricket played? That score sounds like it will be a monster. And 30 innings? Wow, talk about stamina!

More basic algebra. The first 20 innings the cricketer made 300 runs (20 times 15).

Ten innings later (20 + 10 = 30) the average was 17, so the player made (30 x 17) 510 runs.

Subtract the two (510 – 300 = 210) to discover he made 210 runs the last ten innings.

Which by dropping the zero (210 / 10 = 21), gives you an average of 21 runs per inning to end up the game.