Inequalities: Worded problems

Examples with solutions for Inequalities: Worded problems

Exercise #1

Writer A writes 35 \frac{3}{5} of the number of pages writer B writes per day. Both of them together write more than 200 pages per day.

What can be said about the number of pages that writer A writes per day?

Video Solution

Step-by-Step Solution

To solve the problem, we need to analyze the inequality involving the pages written by Writers A and B:

First, let xx represent the number of pages Writer B writes per day. Then, the number of pages Writer A writes is given by the expression 35x\frac{3}{5}x.

The problem states that together they write more than 200 pages per day. Therefore, we can set up the inequality:

35x+x>200. \frac{3}{5}x + x > 200.

We need to simplify and solve this inequality:

  • Combine the terms on the left-hand side:
35x+55x=85x. \frac{3}{5}x + \frac{5}{5}x = \frac{8}{5}x.

Substituting this back into the inequality:

85x>200. \frac{8}{5}x > 200.

To solve for xx, multiply both sides of the inequality by 58\frac{5}{8} to isolate xx:

x>200×58. x > \frac{200 \times 5}{8}.

Perform the multiplication:

x>10008=125. x > \frac{1000}{8} = 125.

This implies that the number of pages xx written by Writer B should be greater than 125.

Substitute x>125x > 125 back to find the pages written by Writer A:

Pages by A=35xPages by A>35125=75. \text{Pages by A} = \frac{3}{5}x \quad \Rightarrow \quad \text{Pages by A} > \frac{3}{5} \cdot 125 = 75.

Therefore, Writer A writes more than 75 pages per day.

The correct answer is:

More than -75

Answer

More than 75

Exercise #2

Gabriel is 14 years older than his brother Simon.

Given that the sum of their ages does not exceed 35, roughly what is Simon's age?

Video Solution

Step-by-Step Solution

To solve this problem, we will follow these steps:

  • Step 1: Write the equation based on the problem statement.

  • Step 2: Simplify and solve the inequality.

  • Step 3: Identify the range for Simon's age.

Now, let's work through each step:
Step 1: The problem states that Gabriel is 14 years older than Simon, so if Simon's age is S S , Gabriel's age is S+14 S + 14 . Given that the sum of their ages does not exceed 35, we can write: (S)+(S+14)35(S) + (S + 14) \leq 35

Step 2: Simplify the inequality:
2S+14amp;352Samp;35142Samp;21 \begin{aligned} 2S + 14 &\leq 35 \\ 2S &\leq 35 - 14 \\ 2S &\leq 21 \end{aligned} Divide both sides by 2:
S10.5S \leq 10.5

Step 3: Given the inequality, Simon’s age is any number greater than or equal to 0 but less than or equal to 10.5. Since Simon must be a whole number, Simon's possible ages range from 0 to 10.

After reviewing the given choices, the correct answer falls within the range:
Between 0 and 10.5

Answer

Between 0 and -10.5

Exercise #3

Given that factory A produces 13 \frac{1}{3} of the productivity of factory B. Both factories together produce less than 700 cartons of milk per day. What can be said about the production of factory A?

Video Solution

Step-by-Step Solution

To solve this problem, follow these steps:

  • Step 1: Identify that x=13y x = \frac{1}{3} y and substitute into the inequality x+y<700 x + y < 700 .
  • Step 2: Rewrite the inequality as 13y+y<700 \frac{1}{3} y + y < 700 .
  • Step 3: Combine and simplify terms: 43y<700 \frac{4}{3} y < 700 .
  • Step 4: Solve for y y by multiplying both sides by 34\frac{3}{4}: y<525 y < 525 .
  • Step 5: Substitute back to find x x : Since x=13y x = \frac{1}{3} y , x<13×525=175 x < \frac{1}{3} \times 525 = 175 .

Thus, we conclude that the production of factory A, x x , is less than 175 cartons per day.

Answer

Less than 175 cartons per day

Exercise #4

Daniel has a number of sweets.

Mariano has 5 times plus 4 more sweets than Daniel

Iván has 8 times plus 14 fewer sweets than Daniel.

Iván has fewer sweets than Mariano.

What is the possible number of sweets that Daniel has in terms of x?

Video Solution

Step-by-Step Solution

To solve this problem, we'll contemplate the mathematical relationships between the sweets.

  • Step 1: Expression Setup
    Mariano's sweets can be expressed as 5x+4 5x + 4 , and Iván's sweets are 8x14 8x - 14 .
  • Step 2: Inequality Setup
    Given that Iván has fewer sweets, establish an inequality: 8x14<5x+4 8x - 14 < 5x + 4 .
  • Step 3: Solve the Inequality
    Simplify the inequality:
    8x14<5x+4 8x - 14 < 5x + 4
    Subtract 5x 5x from both sides:
    3x14<4 3x - 14 < 4
    Add 14 to both sides:
    3x<18 3x < 18
    Divide by 3:
    x<6 x < 6
  • Step 4: Considering Logical Constraints
    Since sweets represent physical goods, x x must be positive. Therefore, x>0 x > 0 .
  • Step 5: Conclusion
    Combining these inequalities, 0<x<6 0 < x < 6 .

Therefore, the possible number of sweets that Daniel has is 0<x<6 0 < x < 6 .

Answer

0 < x < 6

Exercise #5

Dice 3 numbers.

The first half is greater than the second sum by 5.

twice the third number and other 7 less than that amount.

What can be said about these elements?

Video Solution

Answer

The first is greater by four times of the third and more 14