Calculate Water Height Y in a 150 cm³ Rectangular Prism with 50 ml Liquid

Volume Applications with Base Area Calculation

50 ml of liquid is poured into a rectangular prism with a volume of 150 cm.

The distance between the water line and the top of the rectangular prism is 3 cm.

What is the value of Y, which represents the height of the water?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the water level height Y
00:03 We want to find the volume of the empty box
00:07 Subtract the water volume from the total box volume
00:11 This is the volume of the empty box
00:19 We'll use the formula for calculating box volume
00:22 Width multiplied by height multiplied by length
00:26 We'll substitute appropriate values according to the given data and solve for X
00:33 Isolate X
00:42 This is the box width X
00:49 We'll calculate the liquid volume and find the water level height Y
00:55 We'll use the formula for calculating box volume
00:59 We'll substitute appropriate values according to the given data and solve for Y
01:07 Isolate Y
01:13 And this is the solution to the problem

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

50 ml of liquid is poured into a rectangular prism with a volume of 150 cm.

The distance between the water line and the top of the rectangular prism is 3 cm.

What is the value of Y, which represents the height of the water?

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Calculate the base area of the rectangular prism.
  • Step 2: Use the base area to find the height of the water, Y Y .

Now, let's work through each step:

Step 1: The volume of the rectangular prism is given as 150 cm3^3. Let's denote the height of the prism without any liquid as H H , and the gap from the water line to the top of the prism is 3 cm. Thus, the total height is H3 H - 3 . The water volume given is 50 cm3^3, which means the volume occupied by the air is:

15050=100 150 - 50 = 100 cm3^3.

Since the gap is 3 cm (the height of air column), the base area A A can be calculated as:

A×3=100 A \times 3 = 100 .

This implies A=100333.3 A = \frac{100}{3} \approx 33.\overline{3} cm2^2.

Step 2: Now, to find Y Y (the height of water):

We use the formula for the volume of water in the prism:

A×Y=50 A \times Y = 50 ,

where A=33.3 A = 33.\overline{3} cm2^2. Therefore,

Y=5033.3=1.5 Y = \frac{50}{33.\overline{3}} = 1.5 cm.

Therefore, the solution to the problem is Y=1.5cm Y = 1.5 \, \text{cm} .

3

Final Answer

1.5 cm

Key Points to Remember

Essential concepts to master this topic
  • Volume Rule: Total volume equals occupied volume plus air space volume
  • Technique: Use air space: A×3=100 A \times 3 = 100 to find A=33.3 A = 33.\overline{3}
  • Check: Water height times base area equals water volume: 33.3×1.5=50 33.\overline{3} \times 1.5 = 50

Common Mistakes

Avoid these frequent errors
  • Using water volume to find base area directly
    Don't divide 50 by an unknown height to find base area = circular reasoning! This creates two unknowns (base area and height) with only one equation. Always use the air space with known gap height to find base area first.

Practice Quiz

Test your knowledge with interactive questions

A rectangular prism has a base measuring 5 units by 8 units.

The height of the prism is 12 units.

Calculate its volume.

121212888555

FAQ

Everything you need to know about this question

Why can't I just divide 50 ml by some height to get the base area?

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Because you don't know the height yet! You'd be creating two unknowns (base area and height) with only one piece of information. Use the air space instead - you know its volume (100 cm³) and height (3 cm).

How do I know the air space volume is 100 cm³?

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Simple subtraction! Total volume - Water volume = Air volume
150 - 50 = 100 cm³. The air takes up the remaining space in the container.

What does the 3 cm gap actually represent?

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It's the height of the air column above the water surface. Think of it as measuring from the water line straight up to the top of the container.

Why is my base area a repeating decimal?

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That's normal! 1003=33.3 \frac{100}{3} = 33.\overline{3} is exact. You can work with 1003 \frac{100}{3} or the decimal - both give the same final answer of 1.5 cm.

How can I check if 1.5 cm is really correct?

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Multiply: Base area × Water height = Water volume
33.3×1.5=50 33.\overline{3} \times 1.5 = 50 cm³ ✓
Also check: 33.3×3=100 33.\overline{3} \times 3 = 100 cm³ for air space ✓

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