Brainbox Online Civil Service Review | Day 16 - July 2, 2026

Main ideas / lessons (Civil Service Review)

The video is split into two main segments:

1. Subject–Verb Agreement (Day 16 / July 2, 2026, “Brainbox Online Civil Service Review”)
2. Numerical Ability (percentages/discounts/interest) and Ratio & Proportion

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1) Subject–Verb Agreement

The host repeatedly emphasizes the core method:

• Identify the subject first, then choose the correct verb form based on whether the subject is singular or plural.

• Most decisions follow two “foundation” rules:

  • Rule 1 (SS): Singular subject → verb takes -s form (e.g., he/she/it swims)

  • Rule 2 (PB): Plural subject → verb takes base form (e.g., they swim)

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Subject–Verb Agreement: rules taught

The host reviews 29 rules, focusing on patterns and common exam question triggers (e.g., there/here, fractions, collective nouns, a number vs the number, one of + plural noun, etc.).

Foundations (repeated throughout)

• Rule 1 (SS): If the subject is singular, the verb uses the -s form.
• Rule 2 (PB): If the subject is plural, the verb uses the base form.

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Rules 11–20 (explicitly covered in detail)

• Rule 11: Subjects separated by a verb from phrases like along with, as well as, in addition to, including (etc.) do not change the subject’s number.

  • The verb agrees with the main subject, not with the noun inside the extra phrase.

• Rule 12: A phrase after the subject (and similar add-ons) does not change the subject’s number.

  • Verb agreement is based on the subject only.

• Rule 13: Sentences starting with there or here:

  • Identify the following noun (the real subject) and make the verb agree with it.

• Rule 14: Pattern for there is / there are:

  • There is + singular subject noun
  • There are + plural subject noun

• Rule 15: It (as a sentence starter) is followed by the -s verb form (similar agreement trigger to he/she/it).

• Rule 16: Collective nouns are usually treated as singular (one unit) → -s form

  • Exemption: If the collective noun is shown as separate/individual actions or divisions, use plural logic → base form.

• Rule 17: A number takes base form of the verb.

• Rule 18: One of + plural noun takes the -s form (because it refers to one item).

• Rule 19: Expressions of money, time, measurement take the -s form.

• Rule 20: Titles / story names / organizations / countries take the -s form even if they end in -s (because they refer to one).

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Rules 21–29 (covered later)

• Rule 21: Nouns that end in -s but are singular in meaning take -s form of the verb (examples listed: mathematics, economics, politics, ethics, dramatics).

• Rule 22: Nouns that are always plural in form take base form.

  • Examples: pants, trousers (always treated as plural form)

• Rule 23: Nouns that are always singular in form take -s form.

  • Examples listed: bread, furniture (the host also notes common confusion about plural forms)

• Rule 24: “The + adjective” used as a noun takes the base form of the verb.

  • Pattern: the poor/rich + base verb

• Rule 25: Fractions:

  • If the noun after of is singular → -s form
  • If the noun after of is plural → base form

• Rule 26: All of / some of / most of / a lot of / none of depend on the noun type:

  • With plural count nouns → base verb
  • With mass nouns (uncountable) → -s form

• Rule 27: Don’t vs doesn’t:

  • Use “don’t” with plural subjects and pronouns I, you, we, they
  • Use “doesn’t” with singular subjects: he, she, it

• Rule 28: This or that → -s form (singular subject)

  • These or those → base form (plural subject)

• Rule 29: many vs much:

  • many = plural → base form
  • much = singular → -s form

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Method emphasized during practice

For each item, the host instructs viewers to:

• Determine which rule applies (often by spotting keywords like: there/here, collective noun, a number, one of, fractions, money/time/measurement, none of/all of, don’t/doesn’t, this/these, many/much).
• Then apply either:
  • SS vs PB, or
  • the specific rule’s exception/trigger.

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2) Numerical Ability (percentages, discounts, interest)

Combined percent increase/decrease

• Apply changes step-by-step:
  • First compute the increased value.
  • Then apply the decrease to that new value.
• Do not combine percentages directly into one operation.

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Discounts (definitions and rate)

• Terms:

  • Original price = old value
  • Discount amount = actual money subtracted (not a “rate” by itself)
  • Selling price = new value after discount

• If discount rate is needed:

  • Discount rate = ((\text{discount amount} \div \text{original price}) \times 100\%)
  • Use the complement concept when interpreting remaining percent (the host warns against misreading percent meaning).

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Simple interest

• Core formula:

  • Simple interest = principal × rate × time

• Rate/time details:

  • If interest is annual, time is in years.
  • If interest is monthly, interest applies 12 times per year.
  • If time is in months but the rate is annual, convert months to years (or use the appropriate fraction of a year).

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Interest problem handling

• Find interest rate by rearranging.
• Convert interest to decimal form for correct percentage interpretation.
• Emphasis:
  • Practice long division and decimal conversion.
  • Common confusion: whether the time unit matches annual vs monthly interest.

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3) Ratio and Proportion

Ratio basics

• A ratio compares two quantities.
• Written with colon or as a fraction (e.g., 3:2 or 3/2).
• Order matters:
  • 2 apples to 3 oranges ≠ 3 apples to 2 oranges

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Equivalent ratios

• Equivalent ratios have the same simplified structure.
• Create equivalent ratios by multiplying all terms by the same factor.

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Simplifying ratios

• Use GCF (greatest common factor) and divide both parts by it until simplest.

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Proportion types taught

• Direct proportion

  • When one quantity increases, the other increases (same direction).
  • Solved via:
    • equivalent ratios with multipliers, and/or
    • cross-multiplication

• Inverse proportion

  • When one increases, the other decreases (opposite directions).
  • Solved by multiplying within the ratio relationship (the host distinguishes the method from direct proportional cross-multiplication).

• Partitive proportion

  • Given a ratio and a total, find each part.
  • Steps:
    1. Add the ratio terms to get the “parts total”
    2. Divide the overall total by that sum → multiplier per ratio-unit
    3. Multiply the multiplier by each ratio term to get actual quantities

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Main takeaways across both topics

• Grammar: Always locate the true subject, then apply the correct rule (SS vs PB + exceptions).
• Math:
  • For percentages, compute sequentially
  • For interest, use the correct time unit
  • For ratios/proportions, choose the correct proportion type and method

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Speakers / sources featured

• Sir Mark — main instructor/host for subject–verb agreement and math instruction
• Sir JM — referenced by the host (implied co-host/partner); no direct speaking lines provided