RBI GRADE B 2026
Updated June 2026
Master Percentages for
RBI Grade B Phase 1
The complete, no-fluff guide with pro shortcuts, real PYQs, and a 7-day action plan to dominate Quant.
Used by 4,200+ aspirants
Average solve time
38s
Questions in Phase 1
2–5 direct/indirect
Accuracy target
90%+
Based on
2018–2025 PYQs
SECTION 01
Must-Memorize Equivalents
Memorize in 15 mins
| Fraction | Decimal | Percentage | Best Used For |
|---|---|---|---|
| 1/2 | 0.5 | 50% | Halving, quick 50% |
| 1/3 | 0.333… | 33.33% | Recurring — very common |
| 1/4 | 0.25 | 25% | Quarter, easy mental |
| 1/5 | 0.2 | 20% | One-fifth |
| 1/6 | 0.1666… | 16.67% | Recurring |
| 1/8 | 0.125 | 12.5% | Divide by 8 instantly |
| 3/8 | 0.375 | 37.5% | 3 × 12.5% |
| 7/8 | 0.875 | 87.5% | 7 × 12.5% |
| 1/10 | 0.1 | 10% | Base for breakdown method |
| 1/20 | 0.05 | 5% | Half of 10% |
Pro tip: For 17% → break as 10% + 5% + 2%. For 37% → 3 × 12.5%
SECTION 02
Core Formulas
Percentage Increase / Decrease
[(New − Original) / Original] × 100
Use for: Price, salary, population changes
Net % Change (Successive)
a + b + (a × b) / 100
Better: Use Multiplier Method for accuracy
Reverse Percentage (Find Original)
Original = Final ÷ (1 ± r/100)
Most important reverse technique in RBI
Product Constancy
If A increases by x%, B decreases by [x/(100+x)]%
Perfect for Speed-Time, Price-Quantity
SECTION 03
8 Killer Shortcuts
Used by toppers to save 10–15 seconds per question
1
10%-5%-1% Breakdown
Split any percentage into 10% + 5% + 1% for instant mental math.
Example: 47% of 200 = (4×10%) + (7×1%) = 80 + 14 = 94
RBI Hack: Great for DI approximations
2
Cross Percentage Swap
x% of y = y% of x. Swap when it makes calculation easier.
Example: 18% of 50 = 50% of 18 = 9
3
Doubling & Halving
20% = 2×10%, 5% = ½×10%, 40% = 2×20%.
Example: 5% of 300 = ½ of (10% of 300) = 15
4
Multiplier Method (Successive %)
Best method for accuracy with 2 or more changes.
Example: +10% then −5% → ×1.1 × 0.95 = ×1.045
Recommended for 3+ changes
5
Fractional Equivalents Magic
12.5% = 1/8, 16.67% = 1/6 instantly.
Example: 87.5% of 1600 = 1600 − (1600 ÷ 8) = 1400
6
Reverse Percentage
After x% decrease → Original = Final ÷ (1 − x/100)
Example: ₹45 after 25% decrease → 45 ÷ 0.75 = ₹60
7
Smart Approximation (DI)
Round to nearest 5% or 10%, calculate, then adjust.
Extremely useful when options are close
8
Error Percentage
(Error / Correct Value) × 100
Example: Measured 105 instead of 100 → 5% error
SECTION 04
Solved Examples
EX 01
Basic Calculation with Fraction Shortcut
An agent sells goods worth ₹15,000 and gets 12.5% commission. What is the commission?
Solution: 12.5% = 1/8
Commission = 15,000 ÷ 8 = ₹1,875
EX 02
Successive Changes (Multiplier Method)
Book price increases 10%, then decreases 5%. Find net change.
Assume ₹100 → ×1.1 = ₹110 → ×0.95 = ₹104.5
Net change = +4.5%
EX 03
Multi-Step Reverse Percentage
A man loses 20% of his money, then spends 25% of the remainder. He is left with ₹480. Find the original amount.
Let original = x
After 20% loss → 0.8x
Left with 75% of 0.8x = 0.6x = 480
x = 480 ÷ 0.6 = ₹800
SECTION 05
Practice Questions
10 high-yield questions (mix of difficulty). Attempt first, then check solutions.
01
50% of (x − y) = 30% of (x + y). What % of x is y?
Show Solution
0.5(x − y) = 0.3(x + y) → 0.2x = 0.8y → y/x = 0.25 → 25%
02
One-eighth of a number is 17.25. What is 73% of that number?
Show Solution
Number = 17.25 × 8 = 138
73% of 138 = 138 × 0.73 = 100.74
73% of 138 = 138 × 0.73 = 100.74
03
Salary increases by 10% every year. In June 2011 it was ₹22,385. What was the salary in June 2009?
Show Solution
2011 = 2009 × (1.1)² → 22,385 = x × 1.21 → x = ₹18,500
04
Numerator increased by 400%, denominator increased by 500%. New fraction = 10/21. Find original fraction.
Show Solution
New = 5x / 6y = 10/21 → x/y = 4/7
05
A travels from P to Q at 40 km/h and returns at 50% faster speed. Find average speed for the round trip.
Show Solution
Return speed = 60 km/h
Average = (2 × 40 × 60) / (40 + 60) = 48 km/h (Harmonic mean)
Average = (2 × 40 × 60) / (40 + 60) = 48 km/h (Harmonic mean)
06
A number multiplied by 7 is as much above 260 as the original number is below 260. What is 32% of the original number?
Show Solution
7y − 260 = 260 − y → 8y = 520 → y = 65
32% of 65 = 20.8
32% of 65 = 20.8
07
Numerator of a fraction increased by 25%, denominator increased by 20%. New fraction = 5/6. Find original fraction.
Show Solution
1.25x / 1.2y = 5/6 → x/y = 4/5 or 0.8
08
Maya’s salary is 60% more than Swevi’s. Their EMIs are equal. Swevi’s EMI is 20% of her salary = ₹30,000. Maya’s EMI + rent = half her salary. Find Maya’s savings.
Show Solution
Swevi salary = ₹1,50,000 → Maya = ₹2,40,000
EMI = ₹30,000. Rent = ₹90,000. Total expenses = ₹1,20,000
Savings = ₹1,20,000
EMI = ₹30,000. Rent = ₹90,000. Total expenses = ₹1,20,000
Savings = ₹1,20,000
09
Cost of S is 20% more than T. T’s cost = ₹8,000. Transport for S = ₹500. S sold at 12% loss. Find SP of S.
Show Solution
S cost = ₹9,600 + ₹500 = ₹10,100
SP at 12% loss = 88% of 10,100 = ₹8,888
SP at 12% loss = 88% of 10,100 = ₹8,888
10
In an election, 25% did not vote. 1,200 votes invalid. Valid votes = 60,000. A won by 20% of valid votes. Find votes received by A.
Show Solution
Valid + invalid = 61,200 (polled = 75% of total)
Total voters ≈ 81,600. A’s votes = 60,000 + 12,000 = 36,000
Total voters ≈ 81,600. A’s votes = 60,000 + 12,000 = 36,000
SECTION 06
PYQ Trends & Analysis
Most Repeated Patterns
- • Election / Voting problems (reverse % + multi-step)
- • Successive percentage changes
- • Numerator-Denominator fraction changes
- • Reverse percentage with multiple operations
Common Traps in PYQs
- • Base year confusion in “increased by” vs “to”
- • Taking % of new value instead of remainder
- • Not converting recurring decimals to fractions
RBI Trend Insight
RBI loves testing application of reverse percentage and base confusion. Always verify by assuming base = 100.
SECTION 07
Common Pitfalls
“Increased by” vs “Increased to”
Always read the question carefully. “Increased to 150%” means new value is 1.5× original.
Wrong base in successive spend/loss
Never take percentage of the new (reduced) value unless specified.
A is x% more than B ≠ B is x% less than A
Use the formula: B is [x/(100+x)]% less than A.
Calculation errors with recurring %
Use fractions (1/3, 1/6, 1/8) instead of decimals for accuracy.
SECTION 08
7-Day Percentages Mastery Plan
D1
Memorize equivalents + basic formulas (30–40 min)
D2
50 basic % questions (focus on speed)
D3
Master all 8 shortcuts + 30 shortcut-based questions
D4
20 successive & reverse % questions
D5
Full practice set (this page) + PYQs
D6
Mixed DI + % questions from full mocks
D7
Revision + timed 30-question Quant sectional test
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