60-Second Challenge: How Fast Can You Find the Missing Number in These 6 Puzzles?

September 7, 2019 Updated: September 7, 2019

Almost all of us are aware of the importance of mathematics in our daily life. From shopping to cooking, and including personal finance, we make use of it.

However, math isn’t just used for filing taxes; studies have also shown that “cognitive training,” using puzzles to keep your brain sharp, can have all kinds of benefits as you get older. According to a 2014 study funded by the National Institutes of Health, the benefits of cognitive training can last up to 10 years later. The director of the National Institute of Aging explained that brain training can “help maintain the mental abilities of older people so that they may remain independent and in the community.”

Here are six puzzles that will challenge your speed and reasoning skills. Can you find the missing numbers in each set within 60 seconds? This will show how quickly your brain can work in a crunch. So set the timer and get ready to train your brain.

Round 1.

At first, you might have trouble with this one. After all, when it comes to the double-digit numbers, from 10 to 28, all three lines have six numbers in total. And if you subtract 10 from 28, you get 18. So what number could possibly be missing? But that would be counting exclusively, the way we do it for measuring a distance or time, leaving out the first number, in this case 10.

We need to count inclusively, including the number 10. So there should be 19 numbers altogether. Notice that the difference between the first and second set of double-digit numbers is 6. (10+6=16, 11+6=17, 12+6=18, and so on). But when we get to sets 2 and 3, something is off. 23-17=6, so it looks like the pattern is continuing logically. But 25-18=7… and that’s it! The missing number is 24.

Round 2.

Here too, it looks there’s no number that is missing, as the third and fourth sets have equal numbers. But once again, we can spot the skipped number by subtracting. 12-9=3, but then 14-10 and 15-11 both equal 4. So the missing number is one that many people find unlucky. That’s right, it’s number 13.

Round 3.

How about this one? This time everything seems to add up. The difference between the numbers in sets 1 and 2 is 5. The difference between sets 3, 4, and 5 is 4. (12+4=16, 16+4=20, etc.). So what could be missing? If we look at the final number, though, 23, we realize that there are only 22 numbers on the page. Something’s not right. There it is; the number 11 is missing.

Round 4.

Wow, here’s a long one. Once again, everything looks symmetrical. Here too by counting the intervals between numbers, we quickly realize that something is wrong. The pattern for set 3, 4, 5, and 6 should be as follows: add 5, add 5, add 6. Except we notice that the pattern doesn’t work all the way down the line, tipping us off to the fact that something’s off.

Sure enough, 17+5= 21, not 22, as we see. 22+5=27, not 28. So we see that something had been skipped. That’s right, the number 27 is missing.

Round 5.

Now that you’ve got the hang of it, you can probably spot with relative ease that the number 19 is missing from this long set. You can see that set 5 has too many numbers relative to set 6, which follows it. That’s because 19 was left out earlier.

Round 6.

Well, the last two sets definitely don’t look right. See number 37 is hanging out on its own. But that’s a red herring, because the actual missing number is much further up. It’s 24!

To sum up, the missing numbers were the following:

1. 24
2. 13
3. 11
4. 27
5. 19
6. 24

If you managed to get through all of these in 60 seconds, it says a lot about how quickly your brain works.

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