Maths Olympiad Prep

Library / /18 of 241

, 2022

Algebra Difficulty 1.1 Junior Find the answer Canada

Which of the following fractions has the greatest value?

Pick one

Solution

The fractions 310\frac{3}{10}
and 523\frac{5}{23} are each less than
12\frac{1}{2} (which is choice (E))
so cannot be the greatest among the choices. (Note that $12=510=11.523$\$\frac{1}{2} = \frac{5}{10} = \frac{11.5}{23}\$ which we can use to compare the given fractions
to 12\frac{1}{2}.)

The fractions 47\frac{4}{7} and 23\frac{2}{3} are each greater than 12\frac{1}{2}, so 12\frac{1}{2} cannot be the greatest among
the choices.

This means that the answer must be either 47\frac{4}{7} or 23\frac{2}{3}.

Using a common denominator of $3 ×\times 7 =
21,werewritethesefractionsas, we re-write these fractions as 47=1221\frac{4}{7} = \frac{12}{21}and and 23=1421$\frac{2}{3} = \frac{14}{21}\$ which shows
that 23\frac{2}{3} has the gretest
value among the five choices.

(Alternatively, we could have converted the fractions into decimals and
used their decimal approximations to compare their sizes.)

Want a route through all this instead of an archive? The track puts 2,444 problems in a working order, from Junior Challenge level to the IMO shortlist.

Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.