Are You a Master of Mental Math?


By: Robin Tyler

6 Min Quiz

Image: Willie B. Thomas/DigitalVision/Getty Images

About This Quiz

A master of mental math. That is what we are looking for. 

Do you ride past cars on the highway and add the numbers of their registration plates together?

Or do you stare at the barcodes on products, only to find yourself adding and subtracting the numbers you see? Or instead of counting sheep to fall asleep, do you add, multiply or divide them?

If you love numbers, long math word problems, square roots, division signs, multiplication and the like, then this quiz will certainly be a test of your mental math capability. 

Remember at school when others were crunching away on their pocket calculators for the answer, whereas for you, it just popped into your head? Well, you're going to need all of that skill today.  This test is for mathletes and mathletes only. 

Only real masters of math need try it!

So what can you expect? Well, we have 35 questions ranging from very easy to downright difficult, all of which will push your math knowledge to the core. Not to worry, you certainly should be able to score at least 25 out of 35 if you are the expert you say you are!

No pressure then!

So what are you waiting for mathlete, dive right in! 

Let's start of nice and easy shall we. What is 550÷11?

Simple really, 550 ÷ 11 is 50. Why? Well, 550 divided by 10 would be 55, so divided by 11 it's 50.



Take 4x2 and you have 8? It's just 100 times that as it is 40x20. So the answer is 800.


If you had 33 apples and you lose 17, how many apples do you have?

Simple subtraction. 17-16 is 13. Keep better care of your apples, please!


Which number am I? I am found in the range between 20 and 30 and I am a multiple of both 3 and 4.

Easy, it's 24. Why? Because 24 can be divided by both 3 and 4 and it falls into the range of 20 to 30 as requested in the question.


If a doctor asks me to take a pill every quarter of an hour, how many would I have taken between 11 a.m. and 1.01 p.m.?

It's 9 tablets. Let's break it down. You would take at 11 a.m., 11:15 a.m., 11:30 a.m., 11:45 a.m., 12 p.m., 12:15p.m., 12:30 p.m., 12:45 p.m. and 1 p.m.


What is half of 35?

Well 18 and 18 is 36, so half of 36 is 18. That simply enough. 17 and 17 is 34, so therefore half of 35 must bet 17.5. Hmm, that's a roundabout way to get there but it makes sense, doesn't it?


What is 65x3x0?

Anything times zero is zero! The answer is 0. This is a very basic rule of math taught to students at an early age. I hope you remembered it.


What is 5% of 150?

The answer is 7.5%. How do we get that. Ok, 10% of 150 would be 15. Seeing that 5% is half of 10%, we must half 15 to get the answer, which is 7.5.


Of this, which is the largest? 0.91, 0.89, 0.093, 0.9

The first thing to take note is if there are any zeros after the decimal, if there are then these numbers are the smallest. Then it is just a case of treating them like normal numbers. For instance, 0.91, we can see as 91 which is bigger than 89 (or 0.89) and 90 (0.9). The other numbers we dealt with.


What is 0.6 x 6 equal to?

If you multiply the 6's you get the gist of the answer. 6 x 6 would be 36, so 0.6 x 6 must be 3.6. Or add them. 0.6 plus 0.6 is 1.2, plus 0.6 is 1.8 and so on.


If a train leaves the station at 21:00 and travels at 30 miles per hour, how long will it take to reach a station 90 miles away and what time will it arrive?

The answer is 3 hours, 00:00. It travels at 30 miles per hour so it will cover 90 miles in three hours, which would also make the time 00:00.



Well, breaking it down sees 200 times 10 equalling 2000. That's simple enough. Do that twice and add and you get 4000.



The 200 immediately stands out of all the answers. 200 times 5 is 1000. So 1000 divided by 5 is 200. It works the same either way.


Are the two other angles in a isosceles right-angled triangle always both 45 degrees?

An isosceles triangle will have one angle of 90 degrees. All the sides of the triangle are equal in length. This means that the other two angles must both be 45. The total amount of a degrees in this triangle would be 180.



A little bit of a tough one here. But we know that 20 times 20 is 400. So 20 times 22 must be 440. And therefore 440 divided by 22 must be 20.


What is the value of x if x +19 = 39?

The easiest way to find the value of x is to subtract 19 from 39. And the answer is 20. Quite simple, really, but yes, that wasn't a very difficult 'solve for x' question was it?



Add 733 and 200, rounding up the 191. That will give you 933, then you must minus 9 for the rounding up and that leaves 924. How did you work it out? Did you use the same method?


What is the square root of 81?

So we have to ask ourselves, to solve this, we need a number multiplied by itself that is 81. And if you know your 9 times table, it's staring you in the face. 9 times 9 is 81. So the square root of 81 is simply 9.



Let's start with the big numbers. We see 900 next to -899 so that leaves us with 1. 1 plus 99 plus 47 - 10 is 137. And finally, add 137 to 79. So that is 130 plus 70 and 7 plus 8, which is 215.


Bob has a $100 bill. Fred has a $20 bill and five $10 bills. Who has the most money and how much more do they have?

Bob has $30 more than Fred. Why? Well, Bob only has one $100 bill. Fred has 5x$10 ($50) and a $20. Add them together and you have $70 in total for Fred. So now it is easy to see that Bob has $30 more than Fred.


What is 0.6+1.4 equal to?

OK, add it this way. 6 and 4 is 1 plus the 1 left over from the 0.4 and in total it is 2.0. Makes sense, doesn't it?



35 plus 44 is easy added. 3 plus 4 is 7 and 5 plus 4 is 9, so it's 79. Now subtract that from 98 and you get 19. And that is your answer!


If you have 32 lemons, add 27 apples and 4 bananas, how many lemons do you have?

You still have 32 lemons. READ the question carefully! Sometimes math is not just about the numbers, it's about understanding what is expected of you. Now that will keep you on your toes!


What is 0.7 x 3?

The easiest way to get to the answer is to take 0.7 add another 0.7, which is 1.4 and a further 0.7 which is then 2.1. Can you see the correlation where 7 times 3 is 21?



The answer is 341. How? Well a 1000 minus 829 leaves you with 171. Then add 150 which is 321. If you take 80 from 100 you have 20, so add that to the 321 and it becomes 341! Yay!


There are 12 inches in a foot. How many inches in 6 and a half feet?

12 x 6 + 6 will give you your answer and it is 78. Why plus 6. Well, that is the half a foot the question asked to add.



Very easy, with straightforward numbers like 200, it's just simple math. 900 minus 700 leaves 200, but don't forget about the 28 which you must add back to get the full answer.


Bob pays $25 for paint. He buys two tins. The red tin costs $7 more than the blue tin. How much do each of the tins cost?

The red tin is $16, the blue tin is $9. Why? Well, 16 and 9 make up $25 which is what Bob paid. And 16 - 9 equals 7, which the problem tells us is the difference between the two paint prices.



This one we will do a little differently. -899 plus 99 leaves -800. 1000 minus 800 leaves 200 and add 13 and you have 213, the answer we wanted.


0.1+0.85+ _____ =1

0.1 +0.85 comes to 0.95. All that is needed to make up 1 is another 0.05. That is the answer.



Fairly simple if you break it down. 13 times 10 is 130, then add another 13 as the question asks. Do you agree that that gives you 143?


Bill can run at 15 miles per hour. How far does he run in 30 minutes?

Well if he can run 15 miles in an hour, 30 minutes is half of an hour, so to get the answer, take half of how far he runs in an hour. That leaves you with 7.5 miles. Well done, Bill. That is impressive.



22 times 10 equals 220, that's simple enough. Therefore, 220 divided by 12 must equal 10. Do you agree?


What is the square root of 25

We learned earlier that the square root is a number multiplied by itself to give us an answer. So what number, multiplied by itself, gives us 25. That's 5 and that's your answer!


If x + 220 - 30 = 200, what is value of x?

The answer is 10. How? Well take 220 minus 30, that equals 190. But the overall answer is 200. That makes x equal to 10!.


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