Difference between revisions of "2010 AMC 8 Problems/Problem 21"
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2x &= 480\\ | 2x &= 480\\ | ||
x &= \boxed{\textbf{(C)}\ 240} \end{align*}</cmath> | x &= \boxed{\textbf{(C)}\ 240} \end{align*}</cmath> | ||
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+ | ==Solution 2 (working backwards)== | ||
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+ | On the last day Hui read <math>62</math> pages. Working backwards, she read <math>18</math> pages more (<math>80</math> total). <math>80</math> is <math>\frac{2}{3}</math> of the remaining pages, so the third morning Hui had <math>120</math> pages to read. Add back the <math>15</math> and you find <math>135</math> must be <math>\frac{3}{4}</math> of the remaining pages, so there were <math>180</math> pages on the second morning. Add <math>12</math> more, then <math>192</math> is <math>\frac{4}{5}</math> of the total book, which must be <math>\boxed{\textbf{(C)}\ 240}</math> pages long. | ||
==Video Solution by OmegaLearn== | ==Video Solution by OmegaLearn== |
Latest revision as of 20:54, 23 October 2024
Contents
Problem
Hui is an avid reader. She bought a copy of the best seller Math is Beautiful. On the first day, Hui read of the pages plus more, and on the second day she read of the remaining pages plus pages. On the third day she read of the remaining pages plus pages. She then realized that there were only pages left to read, which she read the next day. How many pages are in this book?
Solution 1(algebra solution)
Let be the number of pages in the book. After the first day, Hui had pages left to read. After the second, she had left. After the third, she had left. This is equivalent to
Solution 2 (working backwards)
On the last day Hui read pages. Working backwards, she read pages more ( total). is of the remaining pages, so the third morning Hui had pages to read. Add back the and you find must be of the remaining pages, so there were pages on the second morning. Add more, then is of the total book, which must be pages long.
Video Solution by OmegaLearn
https://youtu.be/rQUwNC0gqdg?t=1739
~pi_is_3.14
Video by MathTalks
Video Solution by WhyMath
~savannahsolver
See Also
2010 AMC 8 (Problems • Answer Key • Resources) | ||
Preceded by Problem 20 |
Followed by Problem 22 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
All AJHSME/AMC 8 Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.