ExamShortcut
medium importance~2 Q in Tier 127 formulasโšก 15 shortcuts5 subtopics

BODMAS, identity-based fractions, surds and indices, square/cube roots and approximation. These are the fastest marks in Tier 1 โ€” usually 1โ€“2 questions per shift โ€” and the same skills (identities, surd handling) power the algebra questions.

Track record in the exam

avg 1.0 Q / shift2024: 1โ€“2 Q2025: 1 Q

Questions per shift in recent SSC CGL papers.

Test difficulty mix (65 questions)

23 easy34 medium8 hard

Question patterns exams keep repeating

Taken from previous-year papers. If a pattern is marked "very common", expect to see it in your exam.

Mixed sums with 'of' and brackets

very common

A long sum with รท, ร—, brackets and the word 'of'.

Do brackets first, then 'of', then รท and ร—, then + and โˆ’.

'Of' always comes before รท and ร—.

Example

Evaluate 64 รท 4 of 2 + 8 ร— 3.

'of' first: 4 of 2 = 8

64 รท 8 = 8

8 ร— 3 = 24

8 + 24 = 32

Learn this in โ€œBODMAS, 'of', brackets & vinculumโ€ โ†’

Cubes over squares: use the identity

very common

"(15.2ยณ โˆ’ 5.2ยณ) รท (15.2ยฒ + 15.2 ร— 5.2 + 5.2ยฒ)"

Top is aยณ โˆ’ bยณ and bottom is aยฒ + ab + bยฒ. They cancel to leave a โˆ’ b.

For aยณ + bยณ over aยฒ โˆ’ ab + bยฒ, the answer is a + b.

Example

(15.2ยณ โˆ’ 5.2ยณ) รท (15.2ยฒ + 15.2 ร— 5.2 + 5.2ยฒ) = ?

Top is aยณ โˆ’ bยณ with a = 15.2 and b = 5.2

Bottom is aยฒ + ab + bยฒ, so it cancels

Answer = a โˆ’ b = 15.2 โˆ’ 5.2 = 10

Learn this in โ€œAlgebraic identities in numerical simplificationโ€ โ†’

Given x + 1/x, find the squares and cubes

very common

"If x + 1/x = 4, find xยณ + 1/xยณ."

For the square: (given)ยฒ โˆ’ 2.

For the cube: (given)ยณ โˆ’ 3 ร— (given).

Example

If x + 1/x = 4, find xยณ + 1/xยณ.

Cube the given: 4ยณ = 64

That equals xยณ + 1/xยณ + 3 ร— (x + 1/x)

So xยณ + 1/xยณ = 64 โˆ’ 3 ร— 4

= 64 โˆ’ 12 = 52

Learn this in โ€œAlgebraic identities in numerical simplificationโ€ โ†’

Powers with the same base

very common

"2^(x+3) ร— 4^(xโˆ’1) = 128. Find x."

Write every number as a power of the same base (4 = 2ยฒ, 128 = 2โท).

Then make the powers equal.

Example

Solve 2^(x+3) ร— 4^(xโˆ’1) = 128.

4 = 2ยฒ, so 4^(xโˆ’1) = 2^(2xโˆ’2)

Add the powers: (x + 3) + (2x โˆ’ 2) = 3x + 1

128 = 2โท, so 3x + 1 = 7

x = 2

Learn this in โ€œSurds & indicesโ€ โ†’

Remove roots from the bottom of a fraction

very common

"1/(โˆš4 + โˆš3) + 1/(โˆš3 + โˆš2) + 1/(โˆš2 + 1)"

Multiply top and bottom by the same numbers with the middle sign flipped.

In a chain, the middle terms cancel.

Example

1/(โˆš4 + โˆš3) + 1/(โˆš3 + โˆš2) + 1/(โˆš2 + 1) = ?

1/(โˆš4 + โˆš3) = โˆš4 โˆ’ โˆš3 = 2 โˆ’ โˆš3 (bottom becomes 4 โˆ’ 3 = 1)

Similarly: โˆš3 โˆ’ โˆš2 and โˆš2 โˆ’ 1

Sum = (2 โˆ’ โˆš3) + (โˆš3 โˆ’ โˆš2) + (โˆš2 โˆ’ 1)

Middle terms cancel: 2 โˆ’ 1 = 1

Learn this in โ€œSurds & indicesโ€ โ†’

Square root of a number with a root inside

common

"Find โˆš(11 + 6โˆš2)."

Write it as a + 2โˆšb.

Find two numbers that add to a and multiply to b; their square roots add up.

Example

Find โˆš(11 + 6โˆš2).

6โˆš2 = 2 ร— 3โˆš2 = 2โˆš18

Two numbers adding to 11 and multiplying to 18: 9 and 2

โˆš(11 + 2โˆš18) = โˆš9 + โˆš2

= 3 + โˆš2

Learn this in โ€œSurds & indicesโ€ โ†’

Square root, cube root and making a perfect square

very common

"What is the least number to add to 1300 to make it a perfect square?"

Find the perfect squares just below and just above the number.

The gap to the next one is what you add.

Example

Least number to add to 1300 to get a perfect square?

36ยฒ = 1296 (too small)

37ยฒ = 1369 (just above 1300)

1369 โˆ’ 1300 = 69

Learn this in โ€œSquare roots & cube rootsโ€ โ†’

Roots inside roots that never end

common

"โˆš(20 ร— โˆš(20 ร— โˆš(20 ร— ...)))"

Call the whole thing x.

The inside repeats, so replace it by x and solve.

Example

โˆš(20 ร— โˆš(20 ร— โˆš(20 ร— ...))) = ?

Let x = โˆš(20 ร— x)

Square both sides: xยฒ = 20x

Divide by x: x = 20

Learn this in โ€œSquare roots & cube rootsโ€ โ†’

Quick estimates

very common

"Find the approximate value of 29.9% of 1199.8 + 15.02 ร— 23.9."

Round every number to an easy one.

Calculate and pick the nearest option.

Example

29.9% of 1199.8 + 15.02 ร— 23.9 โ‰ˆ ?

29.9% โ‰ˆ 30% and 1199.8 โ‰ˆ 1200, so 30% of 1200 = 360

15.02 ร— 23.9 โ‰ˆ 15 ร— 24 = 360

360 + 360 = 720

Learn this in โ€œApproximationโ€ โ†’

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