There is no single way to do these eyeballing tricks. It depends on your mental math capabilities as well as your comfort level in doing the math during the interview.

Another approach: The revenue jumps from 60 to 80 across 3 years. That is a 33% increase. One could probably know from their multiplication tables that:

• 11 * 11 * 11 = 1331
• OR
• 1.1 * 1.1 * 1.1 = 1.331
• OR
• (1+0.1) * (1+0.1) * (1+0.1) = 1 + 0.331
• OR
• (1+10%) * (1+10%) * (1+10%) = 1 + 33%

Which means that the CAGR across the 3 years is approx. 10%

So your 80 would go on to 88

In which case your approach also works well!

Hi there,

Please please don't look at this problem like it's a math problem in your Calculus class!

This is a business scenario. So, apply business logic.

You should assume y5 would be 10% growth not 5%. This is because your growth has clearly accelerated…in the business world you're not going to have a repeating pattern of CAGR!