Can I put multiple resistors in series to get higher resistance?

If I put 3 1MΩ resistors in series, is that the equivalent of one 3MΩ resistor?

Answer

The short answer: Yes. It's the same.

The current through resistors in series stays the same, but the voltage across each resistor can be different. The sum of the potential differences (voltage) is equal to the total voltage. To find their total resistance:

By Wikipedia

But this the ideal value. In the real word, resistors have tolerances and you have take in count. E.g., tolerance of 10%. The final value can vary between 2.7MΩ to 3.3MΩ.