Question

Сая запланировала прочесть книгу в течении нескольких дней. В первый день она прочитала 20 страниц. Если далее она ежедневно будет читать по 16 страниц в день, то она не успеет прочитать 140 страниц в книге к концу срока. Если же она будет читать ежедневно по 26 страниц, то не успеет дочитать 40 страниц в книге. Сколько страниц в этой книге? Пжжжжжжжжжжжжж помогите​

Answer 1

Ответ:

320

Пошаговое объяснение:

пусть Сая планировала прочитать книгу за х+1 день, а всего страниц в книге = с.

1 случай

• если в первый день она прочитала 20 страниц,
• то в оставшиеся х дней она прочитает х*16 страниц
• и останется ещё 140 страниц →
• 20 + 16х + 140 = с

2 случай

• если в первый день она прочитала 20 страниц,
• то в оставшиеся х дней она прочитает х*26 страниц
• и останется ещё 40 страниц →
• 20 + 26х + 40 = с

Объединяя первый и второй случай получаем,что:

с = 20 + 16х + 140 = 20 + 26x + 40

• Найдём х:

20 + 16х + 140 = 20 + 26х + 40

160 + 16х = 26х + 60

160-60 = 26х - 16х

100 = 10х

х = 100/10

х = 10

• Найдём с:

с = 20 + 16х + 140 = 160 + 16х =

= 160 + 16*10 = 160+160 = 320 (страниц) - в этой книге

Answer 2

Problem Analysis

Saya plans to read a book within a few days. On the first day, she reads 20 pages. If she continues to read 16 pages per day, she won't be able to finish reading 140 pages by the deadline. However, if she reads 26 pages per day, she won't be able to finish reading 40 pages by the deadline. We need to determine the total number of pages in the book.

Solution

Let's assume the total number of pages in the book is x.

According to the given information, Saya reads 20 pages on the first day and then reads 16 pages per day. If she reads for n days, the total number of pages she reads can be calculated using the formula:

Total pages read = 20 + 16n

Similarly, if she reads 26 pages per day for m days, the total number of pages she reads can be calculated using the formula:

Total pages read = 20 + 26m

We know that Saya won't be able to finish reading 140 pages by the deadline if she reads 16 pages per day. Therefore, we can set up the following equation:

20 + 16n ≠ 140

Similarly, we know that Saya won't be able to finish reading 40 pages by the deadline if she reads 26 pages per day. Therefore, we can set up the following equation:

20 + 26m ≠ 40

Let's solve these equations to find the value of x, the total number of pages in the book.

Solution Steps

1. Solve the equation 20 + 16n ≠ 140 for n to find the number of days it would take Saya to read 140 pages if she reads 16 pages per day. 2. Solve the equation 20 + 26m ≠ 40 for m to find the number of days it would take Saya to read 40 pages if she reads 26 pages per day. 3. Use the values of n and m to calculate the total number of pages in the book, x.

Solution Details

1. Solving the equation 20 + 16n ≠ 140 for n: - Subtract 20 from both sides of the equation: 16n ≠ 120 - Divide both sides of the equation by 16: n ≠ 7.5 - Since the number of days cannot be a decimal, we round up to the nearest whole number: n = 8

2. Solving the equation 20 + 26m ≠ 40 for m: - Subtract 20 from both sides of the equation: 26m ≠ 20 - Divide both sides of the equation by 26: m ≠ 0.7692 - Since the number of days cannot be a decimal, we round up to the nearest whole number: m = 1

3. Calculating the total number of pages in the book, x: - We know that Saya reads 20 pages on the first day and then reads 16 pages per day for 8 days. Therefore, the total number of pages read is: 20 + 16(8) = 148 - We also know that Saya reads 20 pages on the first day and then reads 26 pages per day for 1 day. Therefore, the total number of pages read is: 20 + 26(1) = 46 - Since Saya cannot finish reading 140 pages or 40 pages, the total number of pages in the book must be between 46 and 148. - Therefore, the total number of pages in the book is x = 148.

Answer

The total number of pages in the book is 148.