Math Riddles

1,3,4,7,11,18,29,?

Tags

CCSS.HSF.BF.A.2

There is an ordinary coin, Jenny tossed a total of 15 times, each time is head side up. Now Jenny wants to throw it again. Do you know what is the probability of it coming up heads?

Give your anwer in 3 decimal places.

Tags

CCSS.HSS.CP.A.5

There are 4 families living in one building, each with two boys. Among the 4 pairs of brothers, the elder brothers are A, B, C, and D, and the younger brothers are P, Q, R, and S. Someone asked, who is your biological brother?

B said that C’s younger brother is S.

C said D’s younger brother is not R.

A said B’s younger brother is not P.

D said that only S’s brother among the three told the truth. D's words are credible, and the person didn't distinguish them even after thinking about it. Thus, who is C's younger brother?

• P

• Q

• R

• S

The circus trained an antelope and a cheetah to race, running back and forth in a 100-meter straight line. The cheetah runs three meters in one step, and the antelope can run two meters in one step, but when the cheetah runs two steps, the antelope runs three steps. In this case, what might be the result of the race?

• antelope won

• cheetah won

• Nobody won

Tags

CCSS.4.NF.A.2

An old rich man who scoured gold in South America not only scoured a lot of gold but also a lot of diamonds. In order to show off his wealth to others, he decided to use the diamond he found to set a priceless treasure that is unique in the world. He decided to take out a diamond from the safe on the first day; on the second day, take out six diamonds and set them around the diamond on the first day; on the third day, set another circle around it (refer picture) the diamond has become two circles. Every day, there will be one more circle added on it. After doing this for seven days, it became a huge diamond circle. How many diamonds are there in this priceless gem?

Tags

CCSS.HSF.BF.A.2

Six people A~F sit around a hexagonal table (as picture). The seats of A and B have already been filled in the picture. Please fill in the vacancies of others in turn according to the following tips.

1. A sits in a seat on the right hand side of F with two vacancies.

2. C sits directly opposite D.

3. E sits in an empty seat to the left of F.

So, if F is not sitting next to D, who will be the right hand side of A?

• C

• E

• F

• D

• 5112

• 3124

• 1352

• 2151

Tags

CCSS.4.OA.C.5

Four groups numbers is given, that is 12369 258 1456258 123654789.

Find a four digit password.

Tags

CCSS.4.NBT.B.6