Solve Sequential Division: +800÷(-4)÷a=?0 Step-by-Step

Sequential Division with Unknown Variables

+800:4:a?0 +800:-4:a\text{?}0

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:08 Let's start by choosing the right sign.
00:14 Remember, a positive number divided by a negative number is always negative.
00:24 We don't have enough information to find out the sign of the unknown A.
00:30 So, it cannot be determined.
00:32 And that's how we solve this problem!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

+800:4:a?0 +800:-4:a\text{?}0

2

Step-by-step solution

Note that in the first stage we are dividing a positive number by a negative number:

+:= +:-=-

Now the exercise is:

:a?0 -:a?0

Since we don't know whether a is a positive or negative number, we cannot determine the sign.

3

Final Answer

It is not possible to calculate

Key Points to Remember

Essential concepts to master this topic
  • Sign Rules: Positive divided by negative always equals negative
  • Sequential Division: 800 ÷ (-4) = -200, then -200 ÷ a
  • Comparison Check: Cannot determine if -200/a > 0 without knowing a's sign ✓

Common Mistakes

Avoid these frequent errors
  • Assuming you can always compare unknown expressions to zero
    Don't guess whether -200/a is positive or negative without knowing a's sign = wrong comparison! The expression's sign depends entirely on whether 'a' is positive or negative. Always check if you have enough information to determine all variable signs before making comparisons.

Practice Quiz

Test your knowledge with interactive questions

What will be the sign of the result of the next exercise?

\( (-2)\cdot(-4)= \)

FAQ

Everything you need to know about this question

Why can't we just solve this step by step like normal?

+

We can solve the first step! 800÷(4)=200 800 ÷ (-4) = -200 . But then we get 200÷a -200 ÷ a , and without knowing if a is positive or negative, we can't determine the final sign.

What if 'a' is zero?

+

Division by zero is undefined! If a = 0, the expression 200÷0 -200 ÷ 0 has no mathematical meaning, making the comparison impossible for that reason too.

How do I know when a problem has 'not enough information'?

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Look for unknown variables that affect the final result. If the sign or value of your answer depends on information you don't have, then you can't complete the calculation.

Could 'a' be a specific number that makes this solvable?

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The problem gives us 'a' as an unknown variable, not a specific number. Even if we knew a = 5 or a = -3, we'd still need that information stated in the problem to solve it.

What's the difference between '>' and 'cannot calculate'?

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The symbols >, <, = represent specific relationships. 'Cannot calculate' means we don't have enough information to determine which relationship is true.

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