J emailed me this nifty way of making her students solve a math problem (with an incentive) i.e. the answer to the math problem is the password to open the (Microsoft) Excel file.

Lets see whether you are smarter than a 5th grader …

There are 7 girls in a bus
Each girl has 7 backpacks
In each backpack, there are 7 big cats
For every big cat there are 7 little cats
Question: How many legs are there in the bus?
The number of legs is the password to unlock the Excel sheet.
If you open it, add your name and send it on to see who else can unlock it.
This is a real math problem so don’t say that a bus has no legs.
Also assume that there aren’t any other person on the bus except the 7 girls (i.e. there isn’t a bus driver).
If you get the correct answer that’s the password to the spreadsheet (link is below).
Put your name in the column with the names and forward it on, if you were smart enough to get the right answer.

[1] Link to the spreadsheet

If you are really stuck, [2] email me for the answer.

Update: Since I’ve been overwhelmed with people emailing me for the answer (more than 400+ people from over a 1200 downloads), I’ve decided to publish it. [3] Here is the link to the solution. No cheating!