Library / /213 of 371

, 2023

Algebra Difficulty 1.4 Junior Find the answer Canada

Square $WXYZ$ is divided into 100 small identical squares. Some small squares are shaded and some are unshaded, as shown.How many more of the small squares need to be shaded so that 75% of the area of $WXYZ$ is shaded?

Pick one

Solution

Of the 100 small identical squares, 28 are presently unshaded,
and so $100-28=72$ are shaded. So that 75% of the area of $WXYZ$ is shaded, 75 of the 100 small squares must be shaded. Therefore, $75-72=3$ more of the
small squares must be shaded.

Figure for this problem

Want a route through all this instead of an archive? The track puts 2,604 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.