SBI PO Formula Sheet
Ten formulas, what each one is for, and a worked example.
SBI PO tests maths twice: Quantitative Aptitude in Prelims and Data Analysis & Interpretation in Mains. Mains is mostly data interpretation and arithmetic caselets, so the formulas that pay off are the ones you apply inside a DI set.
These ten cover most of both papers, with a worked probability example.
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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
Percentage share
Expression
Part ÷ Total × 100
Use it for
A bar or pie chart category as a share of the whole.
3
Formula
Growth rate (CAGR)
Expression
(End value ÷ Start value)^(1/n) − 1
Use it for
Average yearly growth across several years in a DI table.
4
Formula
Profit %
Expression
(SP − CP) ÷ CP × 100
Use it for
Profit or loss on cost price.
5
Formula
Compound interest
Expression
A = P × (1 + R/100)ᵀ; CI = A − P
Use it for
Interest compounded once a year.
6
Formula
Dividing in a ratio
Expression
Share of A = Total × a ÷ (a + b)
Use it for
Splitting an amount, profit or quantity in a ratio.
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
Combinations
Expression
ⁿCᵣ = n! ÷ [r! × (n − r)!]
Use it for
Selections where order doesn't matter.
10
Formula
Speed, distance, time
Expression
Distance = Speed × Time; km/h × 5/18 = m/s
Use it for
Trains, journeys and unit conversions.
| # | 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 | Percentage share | Part ÷ Total × 100 | A bar or pie chart category as a share of the whole. |
| 3 | Growth rate (CAGR) | (End value ÷ Start value)^(1/n) − 1 | Average yearly growth across several years in a DI table. |
| 4 | Profit % | (SP − CP) ÷ CP × 100 | Profit or loss on cost price. |
| 5 | Compound interest | A = P × (1 + R/100)ᵀ; CI = A − P | Interest compounded once a year. |
| 6 | Dividing in a ratio | Share of A = Total × a ÷ (a + b) | Splitting an amount, profit or quantity in a ratio. |
| 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 | Combinations | ⁿCᵣ = n! ÷ [r! × (n − r)!] | Selections where order doesn't matter. |
| 10 | Speed, distance, time | Distance = Speed × Time; km/h × 5/18 = m/s | Trains, journeys and unit conversions. |
Worked Example: Probability
A bag has 5 red and 3 blue balls. Two are drawn at random. What is the probability both are red?
- 1
Ways to pick 2 red
⁵C₂ = 10.
- 2
Ways to pick any 2
⁸C₂ = 28.
- 3
Probability
10 ÷ 28 = 5/14.
Questions from this exact syllabus. No signup.
Approximate in DI
SBI PO Mains DI options are usually far enough apart that rounding to the nearest whole number gives the answer. Save exact calculation for when two options are close.
FAQs
Which SBI PO paper has more maths?expand_more
Mains: Data Analysis & Interpretation carries more weight and is mostly DI and caselets. Prelims Quantitative Aptitude is shorter but includes arithmetic and DI.
Is probability tested in SBI PO?expand_more
Yes, especially in Mains, often combined with combinations.
Do I need CAGR for DI?expand_more
It helps for growth-over-years questions. Many DI sets ask for an average growth rate.
Next steps
Take a full SBI PO mock testThe whole syllabus, timed and scored like the real paper.