Xiao Ming reads a book, and after 7 days, there is still 1/3 of the book left. In the next five days, he would read 60 pages in total. How many pages did Xiao Ming read on average every day?
After reading a book for 7 days, Xiao Ming still had 1/3 of the book left. This meant that he had read 1/3 of the book and the remaining 2/3 of the book needed to read 2/3 × 7 = 4/3 days. Reading a total of 60 pages in the next 5 days meant that Xiaoming had read (60/5) = 12 pages in these 5 days. Therefore, Xiaoming read an average of 12 pages a day.
Xiao Ming reads a book, reads 15 pages a day, and after 4 days, there are still 3/5 of the book left unread. How many pages is this book?
Assuming that this book has $n$pages, Xiaoming reads $x$pages every day: $$ 4\times 15 = 3/5 \times n $$ The solution is $n = 50$. So this book has 50 pages.
Xiao Ming reads a book, reads 16 pages a day, and after 5 days, there are still 3/5 of the book left unread. How many pages does this book have?
Assuming the book has $x$pages: - Xiao Ming read $5$days and read $16$pages every day, so he read $5/times 16 = 80$pages. - The remaining pages are 3/5 of the book's worth, so there are: $$ x - 5 \times 16 = 3/5 \times x $$ The above formula was simplified to: $$ x = 320 $$ So this book is $320$pages.
Xiao Xin reads a book, reads 12 pages a day, and after 5 days, there is still 40% of the book left. How many pages is this book?
Assuming the book has a total of $x$pages: - How many days did Xiao Xin read the $12$page every day? - Xiao Xin has read $5$for days and has $40 $left. This means that there are still $(40/100)/times 12$pages left. - This book has a total of $x$pages, so there are: $$ 12\times 5 + (40/100)\times 12 = x $$ Solve the equation: $$ x = 80 $$ So the book had a total of $80$pages.
Xiao Ming reads a book 20 pages a day, after three days, he still has five-eighths of the book to read.
The number of pages in this book is 256. Xiaoming reads 20 pages a day, so he can read 24 pages a day. In three days, he could finish reading a book with 256 pages. Therefore, Xiao Ming read a total of 256 pages x 3 = 768 pages in three days. After reading these 768 pages, Little Ming still had 768 pages- 256 pages = 512 pages to read. Little Ming read 512 pages/ 20 pages = 26 days. Therefore, this book had a total of 256 + 512 = 768 pages.
Xiao Ming reads a book. He reads 1/13 of the book every day. After 4 days, there are 90 pages left. How many pages are there in this book?
Assuming that the book has $x$pages, the number of pages that Xiaoming reads on the fourth day is $x$multiplied by $1/13$. Because Xiao Ming had read for 4 days, the number of pages he read plus the remaining pages equals the total number of pages: $$ x + (x \times 1/13) + 90 = x $$ To simplify it: $$ x \times 12 - x \times 1/13 + 90 = 0 $$ Solve this equation: $$ x = 130 $$ Therefore, the book had a total of 130 pages.
If a cockroach reads 16 pages of a book every day, there will still be three-eighths of the book left after five days. How many pages are left?
Xiao Gang reads a story book every day and reads 56 pages. After reading for four days, there are still 3/11 pages left. How many pages is this book?
Let's say the book has $x$pages. Xiao Gang reads $56$pages a day, so the number of pages needed to finish the book in four days is $56/times 4 = 216$pages. The remaining pages are $3/11$of the book, which means that the remaining pages are $216/div3/11 = 80$pages. Because Xiao Gang still needed to read for four days, the total number of pages he needed to read was $80 + 4 = 84$pages. Therefore, the book has a total of $x = 84$pages.
Little Light reads a book. He reads 15 pages a day. After 4 days, he still has 3/5 of the book left. How many pages is this book?
Assuming that the book had a total of $n$pages, then according to the question, Little Light finished reading $15/times 4 = 60$pages in 4 days. The remaining pages are $n - 60$. And because the total number of pages in the book is 3/5 of the book, there are: $$n - 60 = 3/5 \times n$$ The above formula was simplified to: $$n = 225$$ Therefore, the book had a total of 225 pages.
How many pages are there in this storybook? If Xiao Qiang reads 20 pages a day, what if there are 15 pages left in the book after five days?
According to the question, Cockroach read 5 days *20 pages/day =100 pages, and the remaining 15 pages of the book are equal to the total number of pages-100 pages that have been read, so the total number of pages is: 100 pages +15 pages =115 pages. The answer was page 115.
Little Ming read a book. After seven days, there was still a quarter of the book left. In the next five days, he read a total of 120 pages, just enough to finish it. How much did Little Ming read on average every day?
假设这本书有 $n$ 页小明读了 $x$ 天. 根据题意小明读了 $x$ 天后这本书还剩下 $1/4$ 于全书的比例即 $\frac{1}{4}n = \frac{1}{4}x(n-x)$. 接下来小明读了 $x+7$ 天后这本书还剩下 $1/4$ 于全书的比例即 $\frac{1}{4}x(n-x) + \frac{1}{4}x^2 + \frac{1}{4}x^3 + \frac{1}{4}x^4 + \frac{1}{4}x^5 = \frac{1}{4}n$. 化简得到 $x^5 - 4x^4 + 3x^3 - 12x^2 + 25x - 4n = 0$. 这是一个由 $5$ 个方程组成的线性方程组可以通过特征值或特征方程的方法求解. 特征值计算如下: 设 $a_1 = 1$$a_2 = -2$$a_3 = -3$$a_4 = -5$$a_5 = -1$则特征方程为 $a_1^5 + a_2^4 + a_3^3 + a_4^2 + a_5^1 = 0$. 解得 $a_1 = 1$$a_2 = -2$$a_3 = -3$$a_4 = -5$$a_5 = -1$因此 $x = (-2 + 3i)(-3 + 5i)(-5 + 1i) = 3$即小明读了 $3$ 天. 因此小明读这本书平均每天读 $3$ 页.