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Word problemsArithmeticMiddle schoolabout 0:51

Five times a number minus 4 equals 21. What is the number?: animated lesson

A narrated, step-by-step word problems video lesson with captions. Final answer: The number is 5.

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Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.3 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Worked example
Five times a number minus 4 equals 21. What is the number?
2. Step by step
1. Read the problem
2. Solve the linear equation
3. The answer
$\text{The number is 5}$
The number is 5
4. Check
- Substitute x = 5: (5)*(5) - 4 = 21 ✓

Transcript

The problem. Here is the problem: Five times a number minus 4 equals 21. What is the number? Let x be the number: “5 times a number minus 4” becomes (5) times x minus 4.

Step by step. Read the problem. Let x be the unknown number. “5 times a number minus 4 is 21” translates to (5) times x minus 4 equals 21. Solve the linear equation. 5x minus 4 equals 21 → x equals (21 plus 4) / 5 equals 5.

The answer. So the answer is The number is 5. Let x be the number: “5 times a number minus 4” becomes (5) times x minus 4.

Check. Substitute x equals 5: (5) times (5) minus 4 equals 21, which checks out.

About word problems

Turn everyday situations about prices, speed, ages and interest into equations and solve them.

Five times a number minus 4 equals 21. What is the number?