He redid the job three times.

This angle is 90 degrees.

I have recently started a new job.

In French, the partitive article plays a very important role.

The greater part of the time is spent on work.

This project was partially successful.

It's difficult to calculate the sum of this convergent series.

Understanding geometric series is important for understanding mathematics.

The harmonic series continues indefinitely, but its sum is not finite.

Problems about arithmetic series often appear in math tests.