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Mathematics

Real number system and number properties — ACT practice questions

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What this topic is

Questions on Real number system and number properties test how numbers behave rather than long calculations.

Typical skills include knowing that an even number times any integer is even, that an odd number plus an odd number is even, and that numbers which are multiples of two values at once are the multiples of their least common multiple. Distance on a number line is another favorite: moving from negative two to five covers seven units, because distance is never negative.

ACT Mathematics often phrases these items as what must be true, and testing a few small numbers, including negatives and zero, quickly rules out choices that only work sometimes.

Sample questions

Pick an answer to see whether it is right — nothing is saved, and nothing needs an account.

Question 1Easier

If m is an even integer and n is an odd integer, which of the following must be odd?

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Answer: D — m+n

An even integer plus an odd integer is odd, so m+n must be odd. Each other expression contains an even factor.

Question 2Mid

A museum tour offered a free map to every 16th guest and a free pin to every 24th guest. Given that 960 guests entered during the day, how many guests received both a free map and a free pin?

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Answer: B — 20

lcm⁡(16,24)=48. Then ⌊960/48⌋=20.

Question 3Easier

A cart starts at −3 on a number line, moves to 8, and then moves to −6. What total distance does the cart travel?

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Answer: D — 25

The two distances are ∣8−(−3)∣=11 and ∣−6−8∣=14. Therefore, the total distance is 11+14=25.

Every question is picked for where you are right now, wrong answers come back until they stick, and it all works offline.

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