Brain Teasers
Valentines
Every student in a second grade class sends a valentine to each of the other students in the class, for a total of 306 valentines. How many students are in the class?
Answer
18 studentsHide Answer Show Answer
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It took me a couple of minutes to find the answer, but, I got it.
I'm glad I paid attention in math class.
I'm glad I paid attention in math class.
At first, when I saw this teaser, I was like, "I'm supposed to be able to solve this?!?!?!?!?" Then I actually did get it! I love this teaser! Keep 'em coming!
OOPS I meant to put some of these in my comment !!!
ur title attracted me, i was curious at wut the teaser was! =P its cute! valentines 4 everyone!
couldnt work this one out at all fun to do tho
couldnt work this one out at all fun to do tho
couldnt work this one out at all fun to do tho
Tricky until I remembered how to solve with combinations
I got it in literally about three minuites!! Im sooooo smart!
I got it in 1 min, basically, if theres n ppl, then they each send n-1 cards, so
n(n-1)=306, so n^2-n-306=0
since 18^2=324, then 17*18=306,
so (n-1(n+17)=0
So must be 18 students
n(n-1)=306, so n^2-n-306=0
since 18^2=324, then 17*18=306,
so (n-1(n+17)=0
So must be 18 students
this one was easy
this one really did not require quadratic equation solving. Knowing that n * (n-1) = 306 required to just look at two consecutive numbers who are both factors of 306. So I got in half a minute by straight away dividing by 6 first and 3 later, to get 17 and 18
I got this in under 10 seconds.
The answer would be the smallest integer n where n^2 > 308. Since I memorized all of the squares up to 51x51 when I was in Jr. High, I knew immediately that 308 was between 289 (17^2) and 324 (18^2).
The reason I memorized the squares is because there is a way to easily multiply two numbers in your head if you know the square of the average of the numbers.
The answer would be the smallest integer n where n^2 > 308. Since I memorized all of the squares up to 51x51 when I was in Jr. High, I knew immediately that 308 was between 289 (17^2) and 324 (18^2).
The reason I memorized the squares is because there is a way to easily multiply two numbers in your head if you know the square of the average of the numbers.
simple quadratic equation ... n*(n+1)=306 => n²+n-306 = 0
like it
like it
Fun and entertaining teaser. Took me a few minutes but I got it. I did not use a formula. Each student would have sent one less than the total amount of students in the class. I squared random numbers between 10 and 20 until I got a number just above 306 and than multiplied that number by a number that was one less than it. Thus 18 * 17.
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