Day 13 of 60 · Mon 12 Oct · Daily workbook · CAT in 48 days

Day 13: Simple & Compound Interest + Arrangements Set + Culture & Society RC

Day 13 of the free ThinkCAT 60-day CAT challenge: 5 simple & compound interest questions and 3 spaced-review QA questions, a full arrangements DILR set (4 questions), a culture & society RC passage (4 questions), plus para jumbles and para summary. Every question is a real CAT PYQ.

QA · 8
DILR · 4
VARC · 6
40 minutes
Real CAT questions

Concept card

Simple & Compound Interest

Core formulas

SI = P × R × T / 100; CI amount A = P(1 + R/100)ⁿ
Half-yearly: R/2 per period, 2n periods
CI − SI for 2 years = P(R/100)²
Effective yearly rate, half-yearly compounding = R + R²/400

60-second shortcut · Successive % beats powers

2 years at R%: 2R + R²/100. At 10%: 21% for 2 years, 33.1% for 3. No powers needed.

Trap box

Looks like: 12% compounded quarterly = 12% a yearActually: 1.03⁴ = 1.1255: 12.55% a year
Looks like: SI doubles money in 5 years ⇒ ×4 in 10Actually: ×4 means +300% at 20% a year: 15 years

From the free Arithmetic Formula + Trap Book (PDF).

What's in Day 13

QA: Simple & Compound Interest (5) + 3 spaced-review questions
DILR: Arrangements set, 4 questions
RC: Culture & Society passage
VA: Para Jumbles, Para Summary

Year, slot and question number for each question appear with the answer key after you submit.

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