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How do you check your math answer?

Ronitte Libedinsky, MS
Academic Tutor
Ronitte Libedinsky is an Academic Tutor and the Founder of Brighter Minds SF, a San Francisco, California based company that provides one-on-one and small group tutoring. Specializing in tutoring mathematics (pre-algebra, algebra I/II, geometry, pre-calculus, calculus) and science (chemistry, biology), Ronitte has over 10 years of experience tutoring to middle school, high school, and college students. She also tutors in SSAT, Terra Nova, HSPT, SAT, and ACT test prep. Ronitte holds a BS in Chemistry from the University of California, Berkeley, and an MS in Chemistry from Tel Aviv University.

Ronitte Libedinsky, MS

Academic Tutor

Expert Answer

There are a couple of ways to check your math answer. The easiest way is to plug your solution back into the problem and work backwards to see if you get the right numbers that way. You can also take a look at your answer and see if it makes sense. For example, if you got a very large number for your answer, and you've been working with smaller numbers, you may not have the right solution.

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How do I work out 15% of something?

Donagan

Top Answerer

Convert 15% to 0.15, then multiply it by the number you're working with.

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What is the least number that is divisible by 2,4,5,8 and 10?

Donagan

Top Answerer

It's 40. 40 is 2 x 4 x 5. You don't use 8 or 10 as factors, because they can both be factored into two of the other numbers being considered (8 is 2 x 4, and 10 is 2 x 5).

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3, 10, 19, 30, 42, 58, 75, __ - what's the missing number?

Donagan

Top Answerer

That sequence is neither geometric nor arithmetic, and it shows no other consistent pattern, so the next number cannot be calculated.

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127.50 + 110.25 =237.75. How do you check this?

I_l1ke_gam3s

Community Answer

Either do 237.75 - 127.50 or 237.75 - 110.25. If you get the other addend when you subtract, your answer is correct.

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How do I check my math answer? 3x - 1 = 2x. The answer I get is x=1.

I_l1ke_gam3s

Community Answer

Substitute 1 for x in the original equation. 3(1) - 1 =2(1). So 3 - 1 = 2. That means x does equal 1.

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The area of a 24-meter-long rectangular garden is 480sq.m. Find the perimeter of the garden.

Community Answer

First you have to find the width, which is the area divided by the length. 480 sq m / 24 m = 20 m. The perimeter is twice the length plus twice the width: 2(24) + 2(20) = 48 + 40 = 88 meters.

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How do you convert 0.345 km to meters?

I_l1ke_gam3s

Community Answer

Multiply by 1000. The answer is 345 meters.

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jasmine paid $12 for 4 tarts and 4 cakes. 3 tarts cost as much as 2 cakes. what was the total cost of 7 tarts and 6 cakes?

Community Answer

Let x be the cost of one cake. We're told the cost of 3 tarts is 2x. Since 4 is 4/3 of 3, the cost of 4 tarts is (4/3)(2x) = 8x/3. According to the first statement above, $12 = (8x/3) + (4x) = (8x/3) + (12x/3) = 20x/3. That means x = ($12)(3/20) = $1.80, the cost of one cake. We already know that the cost of 3 tarts is 2x, which is $3.60, so the cost of one tart is $1.20. Therefore, the total cost of 7 tarts and 6 cakes is (7)($1.20) + (6)($1.80) = ($8.40) + ($10.80) = $ 19.20.

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How do you solve 5x+3y=11, and 2x-7y= -12?

I_l1ke_gam3s

Community Answer

These are simultaneous equations. There are several ways to solve them. In this case the easiest way is the elimination method. (See Solve Simultaneous Equations Using Elimination Method . Multiply the first equation by 2 and the second one by -5. You get 10x + 6y = 22, and -10x + 35y = 60. Add the two equations together: 41y = 82, and y = 2. Now plug that y-value into either original equation: 5x + 3(2) = 11. 5x + 6 = 11, and 5x = 5, so x = 1.

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What is 35 ÷ 6?

Community Answer

35 / 6 = 5.833.

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