Ratio and Percentage Shortcuts That Save Exam Time

In banking exams, quant is less about fancy math and more about finishing on time. SBI PO Prelims gives 20 minutes for 35 quant questions. IBPS Mains Data Interpretation sets can take 10–12 minutes each. Every second matters.

These 7 ratio, percentage, and speed math hacks save about 15–20 minutes each paper. We drill them daily in ACIselect's Specialized Quantitative Training — in banking, speed matters for selection.

We help you get ready for government and banking exams at ACIselect in Guwahati. Only 30 students join each batch.

Hack #1 — fraction to percentage, fast recall

Idea: Learn 15 common fractions. Cut long percent work.

Fraction	%	Fraction	%
1/2	50%	1/7	14.28%
1/3	33.33%	1/8	12.5%
1/4	25%	1/9	11.11%
1/5	20%	1/11	9.09%
1/6	16.67%	1/12	8.33%

Solved: Find 16.67% of 720. 16.67% = 1/6 → 720 ÷ 6 = 120 About 3 seconds vs about 45 seconds the long way.

Hack #2 — two percent changes one after another (multiply)

Idea: Do not add the percents blindly. Multiply the growth factors.

Formula: +a% then +b% = ×(1 + a/100) × (1 + b/100)

Solved: Price rises 20%, then falls 10%. Net change? = 1.20 × 0.90 = 1.08 → +8% increase Takes seconds. Trap: students often say +10%.

Hack #3 — match ratios with scaling

Idea: Make one part of the ratios the same number.

Solved: A:B = 3:5 and B:C = 4:7. Find A:B:C.

• First ratio: A:B = 12:20 (×4)
• Second ratio: B:C = 20:35 (×5)
• Together: A:B:C = 12:20:35

Banking: Mixture sums, partnerships, income–spend charts.

Hack #4 — percentage point ≠ percent change

Idea: Examiners use both. Know which one they mean.

• Percentage point: Simple gap (30% → 25% = 5 percentage points down).
• Percent change: (25−30)/30 × 100 = −16.67%

Solved (DI style): Bank A had NPA 8% in 2024 and 6% in 2025. What changed?

• Percentage points: 2 pp down
• Percent change: (8−6)/8 × 100 = 25% decrease

Hack #5 — componendo–dividendo for ratio sums

Idea: If (a+b)/(a−b) = (c+d)/(c−d), then a/b = c/d.

Solved: (x + 5)/(x − 5) = 7/3. Find x. By componendo-dividendo: x/5 = 7/3 → x = 35/3 ≈ 11.67

Banking: Shows in about 1–2 questions per IBPS paper. Saves 60+ seconds when it fits.

Hack #6 — alligation (mixture shortcut)

Idea: Two items at rates A and B mix to average M:

(Cheaper quantity) / (Dearer quantity) = (B − M) / (M − A)

Solved: Mix rice ₹40/kg and ₹60/kg to average ₹48/kg. Ratio? Cheaper : Dearer = (60−48) : (48−40) = 12:8 = 3:2

Banking: Alloys, mixing profit marks, average speed mixes.

Hack #7 — digital sum quick check

Idea: Add digits to check multiplication fast.

Solved: Is 234 × 56 = 13,104 correct?

• Digital sum: 234 → 2+3+4 = 9; 56 → 5+6 = 11 → 1+1 = 2
• 9 × 2 = 18 → 1+8 = 9
• 13104 → 1+3+1+0+4 = 9 ✅

If the sums fail to match → recheck. Helps catch many careless errors in DI.

Time saved — summary

Hack	Questions Per Paper	Avg Time Saved Each	Total Saved
Fraction conversion	5–6	25 sec	2–2.5 min
Successive %	2–3	30 sec	1–1.5 min
Ratio scaling	3–4	20 sec	1–1.5 min
% point vs % change	2	30 sec	1 min
Componendo-dividendo	1–2	45 sec	1 min
Alligation	1–2	40 sec	1 min
Digital sum verify	All DI	5 sec/check	2–3 min
Total			15–20 min

About 15–20 minutes extra means about 10–12 more tries — that shifts results.

4-week practice plan

Week	Focus	Daily Drill
1	Hacks #1 + #4	30 percentage Q
2	Hacks #2 + #3	25 ratio Q
3	Hacks #5 + #6	20 mixture/partnership Q
4	Hack #7 + mixed timed sets	2 full DI sets/day

Lifetime Test Support picks drills after mocks show ratio/percentage slips. Pair with Vedic Maths techniques → for more speed.

Why ACIselect banking quant works

• Specialized Quantitative Training — hacks inside daily class, not "extra sheets"
• Small Batches (max 30) — teacher watches your steps and fixes them
• Lifetime Test Support — micro-tests after each quant class
• Lifetime Test Support — stuck on ratio at night? Ask Lifetime Test Support
• Banking in 90-Day Unified Bootcamp (₹14,999) or 90-Day Unified Bootcamp (₹14,999)

School-style long methods hurt in the hall. Banking quant rewards speed.

Join the banking quant program →