Can You Pass This Basic 2-Digit Number Addition Test Without Using a Calculator?


By: Robin Tyler

5 Min Quiz

Image: shutterstock

About This Quiz

Ok, quick - add 80 and 91, or 11 and 15. Or add another set of numbers, like 80+33 or 91+20. Can you add those up in your head? Do you find mental mathematics easy? 

So you reckon then that you are a bit of a math wizard? Well, you're lucky - some of us need the calculator, even for basic two-digit number addition.

Do you remember back in school when our teachers would tell us the importance of not always relying on your calculator to do the math for you? That it would make you lazy? That you should develop your own system to help you add numbers easily? Well, hopefully, you did. There are many ways to add numbers together in our heads, it's about finding a system that works for you (and if you take this test, we will show you one or two methods that we use).

So let's get right back to the task at hand. Thirty-five questions of basic two-digit number addition. If you are good at this sort of thing, you really will fly through this test in no time at all.

Can you get 100%, though? Sometimes numbers can trick us!

Let's see how you fare! Good luck! 

Add 97 and 45, what do you get?

Easy way to do it: round 97 up to 100, add the 45, then take off the 3 for the rounding up you did. Follow? It's 142.



That's right, 114. Round both the numbers up. So 30 plus 90. That would be 120, then remove the 3 and 3 to get 114.


If you had 36 apples and you added another 45 apples, how many would you have?

Round up the 36 to 40, then add it to 45 to get 85. Then take off 4 for the rounding up. You have 81!


What is 81+89?

8+8 is 16, so 80+80 is 160. Then add 1+9, which is 10. 160+10=170. Just one way to do it.


If you add 39 to 74, what do you get?

The answer is 113. How? Well 39 is close to 40, so you could add 40 to 74, which would be 114, then you have to minus the 1 to get 113.


88 pebbles and another 44 pebbles added means you have ______ pebbles.

132, it's an even number. An easy way to get this answer is to add the first 80 and the first 40 to get you to 120 and then add the remaining 8 and 4 to get 12. Added together, it's 132.



Round 72 down to 70, add 24 to get 94, then add the 2 that you rounded down. That's how you could have gotten to 96. Did you do it that way?


What is the sum of 14+16?

10+10+4+6=30. A different way of adding things... There are many ways to come to the correct answer on a math problem.


Add 52 and 66, and what is the answer?

118, but you knew that! How did you get there? We added 50 plus 60 to give us 110 and then the 2 and the 6 for 118. Easy when you know how!



A simple one. Just turn the 99 into 100, add 21, and then minus the 1 to get 119. But you got that, right?


41 bananas plus another 71 bananas gives you how many bananas?

70 and 40 would be 110, then add the extra 1 and 1 to get 112. So many bananas!


Please add 71 + 89.

The answer is 160. 70 plus 80 is 150, and then add 9 and 1 to get 160.



Too simple! Hey, we gotta give a few easy ones. 30+20 is 50, and then add the 7 and the 1 to get 8. 58 in total.


What does 99 + 92 come to?

Let's get this one in a little different way. 100 plus 100 is 200. So take 1 away for 99 and 8 away for 92. Therefore, the answer is 191. Got it?


The sum of 58+76 is what?

Round up the 58 to 60. Now round down the 76 to 70. Add them together to get 130. You need to take off two for rounding up (58 to 60) and add 6 for rounding down (76 to 70). And that equals 134.


If you have 90 eggs and you add 30 eggs, how many do you have?

You must have gotten this one with ease! It's 120. Just drop the zeros. 9 and 3 is 12, so 90 and 30 is 120.


Tell us what number you get when you add 25 to 75?

Yeah, we bet this one didn't really test you. Both numbers are multiples of 25, and when added together they come to 100.



6 and 1 is 7, then 3 and 8 is 11. So through that little equation, we can see the answer is 81.



Take 75, add 40 and you have 115. Now take off 1 for rounding up to 75 and add 3 for rounding up to 40. And then you have 117. Makes sense, right?


45+88 will equal what?

A little tougher, this one. Did you get 133? Well done. We got there this way. We rounded up 88 to 100, added 45 and then took away the 12 for the rounding up. That is 133. Simple when you know how, right?



Crazy 88! Basic math skills would see you cruise this question. We're going to have make it a little bit more difficult next time.


29 cupcakes plus 54 cupcakes gives you how many?

Tummy ache! Don't eat them all. No seriously, the answer is 83. Make sure you share them around!


Please tell us the sum of 56 and 81?

Well, 5 and 8 is 13, so we know it is 130 something. Add the 6 and 1 and you have 7, so it must be 137!


If you travel 34 miles and then another 76 miles, how far have you gone?

A long way from your starting point! In all seriousness, 30 and 70 is 100, and then add another 4 and 6 which is 10. Altogether, 110 miles.


If you have 66 oranges and you add another 54 oranges, how many do you have?

A hell of a lot of orange juice... if you have the time to squeeze them, that is! Again, the easy way to add this is to take 60 and 50, which is 110, and then add the 6 and 4 which is another 10, giving you 120.



That's an odd number but relatively easy to get to, don't you think? Just round the 98 to 100, add the 87 for 187, then remove the 2 from the rounding up. That leaves you with 185.


Add 21 to 17 and what do you get?

No doubt you nailed this. Its simple math, really. The answer is 38


If you take 14 potatoes and add another 47, what do you have?

The start of a McDonald's franchise? Just kidding. 50 + 14 would be 64, but then take away the 3 for rounding up and you have 61 potatoes!


Add 65 and 65. What have you got?

Too simple! A 5th-grader knows that the answer is 130.



Round up the 91 to 100, add 57 for 157, then minus the 9 from the rounding up. You are left with 148.


What is the sum of 55 and 79?

5 and 7 are 12, so that equates to 120, then add 9 and 5 which is 14, so 120 plus 14 is 134! Easy enough.


Add 36+65?

Just 1 more than 100: 101! And we got there like this. 6 and 5 are 11 and 60 and 30 are 90. Added together, it's 101.


You have 32 pieces of candy and take another 43 from your brother. How many pieces do you have?

The answer is 75 pieces of candy and an unhappy brother. Don't eat them all, that's just going to lead to a sore stomach. And who can eat 75 pieces of candy, anyway?


If you add 33 to 81, what do you have?

30 plus 80 gives you 110. Then add 3 and 1 and you have 114.



Did you get it right? It's 123. You could have gotten there this way. Round up the 89 to 100, add the 34 for 134, then minus the 11 from the rounding up to get 123.


Explore More Quizzes

About HowStuffWorks Play

How much do you know about dinosaurs? What is an octane rating? And how do you use a proper noun? Lucky for you, HowStuffWorks Play is here to help. Our award-winning website offers reliable, easy-to-understand explanations about how the world works. From fun quizzes that bring joy to your day, to compelling photography and fascinating lists, HowStuffWorks Play offers something for everyone. Sometimes we explain how stuff works, other times, we ask you, but we’re always exploring in the name of fun! Because learning is fun, so stick with us!