Math Riddle From A Kenyan Bank

Share it with your friends Like

Thanks! Share it with your friends!


The Cooperative Bank of Kenya, one of Kenya’s largest banks, tweeted out this problem. If 4 + 2 = 26, 8 + 1 = 79, 6 + 5 = 111, then what is 7 + 3 = ? My challenge: if 7 + 3 = z, solve for another pair of numbers x + y = z. Very few can solve this challenge problem!

Cooperative Bank of Kenya tweet

My blog post for this video

Viral Intelligence test 6 + 4 = 210

If you like my videos, you can support me at Patreon:

Connect on social media. I update each site when I have a new video or blog post, so you can follow me on whichever method is most convenient for you.

My Blog:

Newsletter (sent only for big news, like a new book release):

If you buy from the links below I may receive a commission for sales. This has no effect on the price for you.

My Books
“The Joy of Game Theory” shows how you can use math to out-think your competition. (rated 4/5 stars on 34 reviews)

“The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias” is a handbook that explains the many ways we are biased about decision-making and offers techniques to make smart decisions. (rated 4.6/5 stars on 3 reviews)

“Math Puzzles Volume 1” features classic brain teasers and riddles with complete solutions for problems in counting, geometry, probability, and game theory. Volume 1 is rated 4.4/5 stars on 13 reviews.

“Math Puzzles Volume 2” is a sequel book with more great problems. (rated 4.3/5 stars on 4 reviews)

“Math Puzzles Volume 3” is the third in the series. (rated 3.8/5 stars on 5 reviews)

“40 Paradoxes in Logic, Probability, and Game Theory” contains thought-provoking and counter-intuitive results. (rated 4.3/5 stars on 12 reviews)

“The Best Mental Math Tricks” teaches how you can look like a math genius by solving problems in your head (rated 4.7/5 stars on 4 reviews)

“Multiply Numbers By Drawing Lines” This book is a reference guide for my video that has over 1 million views on a geometric method to multiply numbers. (rated 5/5 stars on 3 reviews)


Mythic IQ says:

I used 205+205 for the challenge

I am curious says:

205 + 205 = z should also be a solution


prove that ef||bc in ∆abc .d is mid point of bc . and de and df are bisectors of angle ADB AND ADC ..AD IS MEDIAN OF VERTEX BC…

Solve it without Thales theorem

Ryuga Hideki says:

Try 205+205

moumous says:

So easy… you just offended Kenya and its banking system. I’ll be nice and will not dislike this video… but make more interesting content. These riddles don’t deserve a 5-minute video

Philip Yao says:

I foudn the pattern easily for 7+3=410, but then when I tried finding another solution, I couldn't find it. I used symbolab's matrix which said 3 and 7, I used desmos which also said 3 and 7. But then it hit me, it's not x+y=10 x-y=4. it's x+y=41 x-y=0, then the answer was obvious. x and y both equal 20.5

Andrew Tyberg says:

I was able to figure out both of them.

NeonGiddyVids says:

I looked at thumbnail it’s so ez

Bruno Solaeche says:

It could also be 205+205, because 205+205=410 and 205-205=0, so the number is 205 +205 +0= 410

Urutsini says:

Can the number not also be read as 0410 . . . Which would make another possible answer as 205+205?

chinareds54 says:

Ok. New solution that doesn't involve any of that silly concatenation stuff. The function defined by a{+}b is, in fact, (a+b)^2-2*b+6*cos(b*pi/2). 4{+}2=26, 8{+}1=79, 6{+}5=111. 7{+}3=94. Challenge solution (which I got by blind luck): 7{+}-15=94.

Leonard Wong says:

No wonder Kenya is poor. They complicate the banking sector.

A. Ñeko says:

This was relatively easy.

MrBrain4 says:

I solved both the original problem, and the challenge problem. Very nice question! By the way, I really like how you changed the + to a + with a circle around it, to indicate that it's not really addition, but rather a different operation.

Hot Flash Foto says:

Before looking at the solution, my answer for "7 + 3" is 410. The pattern appears to be subtracting and then adding the second number to the first, and putting the result of each of those together as a single number. 7-3 = 4, and 7+3=10, answer is 410.

Gregg Moorson says:

And also for challenge puzzle for x 3 and 3, for y 2 and 2

Gregg Moorson says:

It's 410

Lukas Dopart says:

Solved in two seconds

John Długosz says:

few can solve? The world is doomed. Why is it so trivial for some of us?

Yash Uppot says:

I guess 104 cos u add the numbers then subtract them

Dreadpirate404 says:

Your solution had a slight mistake! Y=41/2, not -41/2

Aniruddh Vasishta says:

Disclaimer: This is not an original comment. It is a copy+paste of a post by a user named Jess Stuart
I feel like the whole concatenating business is a little cheatsy. I fit the datapoints in the first three equations to a plane, then calculated the height of the plane at (7,3). f(x,y) = (122/7)*x + (117/7)*y – (540/7).

f(4,2) = 26
f(8,1) = 79
f(6,5) = 111
f(7,3) = 95

Milind B. says:

205 + 205 also works.

Patrick A. Crawley says:

Oh….6 seconds.

Darius Sajid says:

Wouldn't x,y = 205 also be a solution to the challenge problem??

MrVlekje5 says:

And 410 + 0 410-0

MrBirdattack says:

205 + 205 = 0410 = 410

same hagerty says:

presh you should've mentioned the possibility of negative numbers, yet you can take the pair
a+b=410 and a-b=0 which gives the solution a =205 and b=205

Alexander Terry says:

Way too easy.

Matthew O'Connor says:

simple pattern
x+y equiv x-y| x+y=z

so 7+3 = 411

Write a comment