Guide 2 - Chapter 1 question 17 - Decimals expression

[alexambroz]

Question 17 (from Chapter 1 in Guide 2 (FDP)):

Which of the following decimals can be expressed as a fraction? (Choose all that apply)

(A) Pi
(B) 0.146 (with a bar over the 146)
(C) 1.398475
(D) Square root of 2

The answer on page 27 says (B) and (C) but it seems like (A) should also be an answer (Pi = 22/7). What am I missing here?

Thanks.

-Alex

[nigerian.horse]

Pi is an irrational number. Hence it cannot be expressed as a fraction. Its is only approximated by 22/7. Its real value is not 22/7, though 3.14 is usually used for mathematical computations.

[Ben Ku]

nigerian.horse is correct ... pi is an irrational number, meaning it cannot be expressed as a fraction. 22/7 is a helpful approximation but is NOT pi.

Decimals that either terminate (2.3567) or repeat indefinitely (2.3535353535...) can be expressed as fractions, and are therefore rational.

Decimals that never terminate but don't repeat (2.112123123412345123456 ...) cannot be expressed as fractions and are therefore irrational. Common irrational numbers include pi and any root that cannot be simplified (ex. sqrt(2))

Hope that helps.

[alexambroz]

Got it. Much appreciated!

[Ben Ku]

Glad it helped.