IBPS PO Formula Sheet
Ten formulas, what each one is for, and a worked example.
IBPS PO maths is increasingly about arithmetic wrapped in data: caselets, missing-value DI and data sufficiency. These ten formulas cover the arithmetic those sets are built from.
A worked boats-and-streams example follows the table.
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The 10 Formulas
1
Formula
Percentage change
Expression
(New − Old) ÷ Old × 100
Use it for
Growth and fall in values, and the base of most DI questions.
2
Formula
Profit %
Expression
(SP − CP) ÷ CP × 100
Use it for
Profit or loss on cost price.
3
Formula
Compound interest
Expression
A = P × (1 + R/100)ᵀ; CI = A − P
Use it for
Interest compounded once a year.
4
Formula
Boats and streams
Expression
Boat speed = (D + U) ÷ 2; Stream = (D − U) ÷ 2
Use it for
From downstream (D) and upstream (U) speeds.
5
Formula
Pipes and cisterns
Expression
Net fill per hour = 1/a − 1/b
Use it for
One pipe filling (a hours) while another empties (b hours).
6
Formula
Partnership
Expression
Profit share ∝ Capital × Time
Use it for
Splitting profit between partners who invested for different periods.
7
Formula
Alligation (mixtures)
Expression
Cheaper : Dearer = (Dearer − Mean) : (Mean − Cheaper)
Use it for
Ratio in which two items are mixed to reach a mean price.
8
Formula
Probability
Expression
P(E) = Favourable outcomes ÷ Total outcomes
Use it for
Balls, cards and dice questions, often with combinations.
9
Formula
Quadratic roots
Expression
x = [−b ± √(b² − 4ac)] ÷ 2a
Use it for
Quadratic-equation comparison questions (x vs y).
10
Formula
Data sufficiency rule
Expression
Check each statement alone first, then together
Use it for
Deciding which statements are enough, without solving fully.
| # | Formula | Expression | Use it for |
|---|---|---|---|
| 1 | Percentage change | (New − Old) ÷ Old × 100 | Growth and fall in values, and the base of most DI questions. |
| 2 | Profit % | (SP − CP) ÷ CP × 100 | Profit or loss on cost price. |
| 3 | Compound interest | A = P × (1 + R/100)ᵀ; CI = A − P | Interest compounded once a year. |
| 4 | Boats and streams | Boat speed = (D + U) ÷ 2; Stream = (D − U) ÷ 2 | From downstream (D) and upstream (U) speeds. |
| 5 | Pipes and cisterns | Net fill per hour = 1/a − 1/b | One pipe filling (a hours) while another empties (b hours). |
| 6 | Partnership | Profit share ∝ Capital × Time | Splitting profit between partners who invested for different periods. |
| 7 | Alligation (mixtures) | Cheaper : Dearer = (Dearer − Mean) : (Mean − Cheaper) | Ratio in which two items are mixed to reach a mean price. |
| 8 | Probability | P(E) = Favourable outcomes ÷ Total outcomes | Balls, cards and dice questions, often with combinations. |
| 9 | Quadratic roots | x = [−b ± √(b² − 4ac)] ÷ 2a | Quadratic-equation comparison questions (x vs y). |
| 10 | Data sufficiency rule | Check each statement alone first, then together | Deciding which statements are enough, without solving fully. |
Worked Example: Boats and Streams
A boat goes 15 km/h downstream and 9 km/h upstream. Find the boat's speed in still water and the stream's speed.
- 1
Boat speed
(15 + 9) ÷ 2 = 12 km/h.
- 2
Stream speed
(15 − 9) ÷ 2 = 3 km/h.
- 3
Check
12 + 3 = 15 downstream and 12 − 3 = 9 upstream.
Real questions from these exact topics. No signup.
Quadratics: Compare Roots, Don't Solve Fully
In x-vs-y questions you only need the roots' signs and sizes. Factorise quickly. If both roots of x are greater than both roots of y, the answer is x > y.
FAQs
Is IBPS PO Mains maths harder than Prelims?expand_more
Yes. Mains Data Analysis & Interpretation uses long caselets and missing-value DI, built on the same arithmetic.
What is data sufficiency?expand_more
Questions that ask whether the given statements are enough to answer, not for the answer itself.
Do quadratic equations still appear?expand_more
Yes, mostly in Prelims, as x vs y comparisons.
Next steps
Take a full IBPS PO mock testThe whole syllabus, timed and scored, in one sitting.