BODMAS and simplification

Story hook

Two friends, Riya and Aman, are sharing the bill at a tea stall. They bought 2 cups of tea at 10 rupees each, plus 1 samosa for 15 rupees.

Riya writes it down like this: 2 × 10 + 15.

Aman, in a hurry, adds first: 10 + 15 = 25, then doubles it: 2 × 25 = 50 rupees.

Riya does the multiplication first: 2 × 10 = 20, then adds 15 to get 35 rupees.

They both used the same numbers, yet got two different answers — 50 and 35. The shopkeeper, of course, charges only the correct one: 35 rupees.

So who is right, and why? The answer is a tiny rule with a funny name — BODMAS — that tells us the order in which to do the steps. Once you know it, you will never be confused by a long line of numbers again. Let's learn it from the very beginning.

Why this matters for UPSC

CSAT (Prelims Paper-II) is a qualifying paper — you only need 33% (about 27.5 marks out of 80) to pass. You don't need to be a maths genius. You just need to not lose easy marks. And "simplification" questions are some of the easiest marks in the whole paper.

• Every CSAT paper has a handful of direct simplification questions: a long string of numbers with brackets, ×, ÷, +, − and you just compute the value. With BODMAS, these are free marks — 30 to 60 seconds each.
• BODMAS is also hidden inside almost every other question — percentages, profit and loss, averages, ratios. If you get the order of steps wrong, even a "hard" topic you studied well will give you a wrong answer.
• In real life it decides your shopping bill, how you split a restaurant cost with friends, and how a calculator or a spreadsheet works out a formula.

Think of BODMAS as the traffic rules of arithmetic. Cars move in a fixed order at a crossing so there is no crash. Numbers get worked out in a fixed order so there is no confusion. Learn the rule once, use it forever.