Approximation and Percentage Skills in DI
The speed skills DI rewards: rounding sensibly before dividing, the fraction equivalents of common percentages, percentage-change shortcuts, and comparing ratios by cross-multiplication instead of full division.
What you will be able to do
- Round each figure to a friendly value before dividing, when the options allow it.
- Recall the fraction equivalents of the common percentages.
- Apply percentage-change shortcuts without writing the full formula.
- Compare two ratios by cross-multiplication rather than dividing both.
What is inside this lesson
- 1Why the arithmetic has to be quick
- 2Fraction equivalents of common percentages
- 3Round, then divide
- 4Percentage-change and ratio shortcuts
- 5Worked example: weekly footfall at five branches
- 6When not to approximate
- 7Quick revision
- 8Practice
Get Pro for full access. This is section 1 of 8; the rest of the lesson opens with Pro at onelystop.in/upgrade.
Why the arithmetic has to be quick
A DI set is five questions in five or six minutes. Most of them do not need an exact answer — the options are spread far enough apart that a close estimate picks the right one. The candidates who finish are the ones who round before they divide, know the common fractions by heart, and compare ratios without long division.
This topic is those habits. The method is the same as ordinary percentages and ratios; only the speed is different.
Reading the 8 sections above is free. A free account opens the first 2 topics of every subject in full, along with flashcards and private notes.