Math Is Fun Forum

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Name the Number

I'm thinking of a number. It lies between 1 and 10. Its square is rational and lies between 1 and 10. The number is larger than pi. Correct to two decimal places (that is, truncated to two decimal places) name the number.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Name the Number

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Name the Number

Bob

At another site, someone responded that the answer is 3.15.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Name the Number

root 10 is bigger than 3.16 so that is another possible answer.  If you round off root 10 before testing the criterion then you would need to exclude 3.16 as an answer, but the question isn't worded like that.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Name the Number

root 10 is bigger than 3.16 so that is another possible answer.  If you round off root 10 before testing the criterion then you would need to exclude 3.16 as an answer, but the question isn't worded like that.

Bob

This is a weird question found in Sullivan's review section R.1.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Name the Number

I've downloaded the pdf and found that question.  What I couldn't find is the answer section relating to the question. The content is excellent but I found the layout hard to follow. Maybe one gets better with practice.

root 10 is 3.1622776601683.....

If you round this to 2dp then you get 3.16 and if our number must be less than 3.16 then only 3.15 works. But that isn't what the question says.

We have to find a number, one property of which is it's less than root 10. Then, and only then, round it to 2dp.  By that logic 3.16 fits too.

Ho hum, never mind; it's a minor point.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Name the Number

I've downloaded the pdf and found that question.  What I couldn't find is the answer section relating to the question. The content is excellent but I found the layout hard to follow. Maybe one gets better with practice.

root 10 is 3.1622776601683.....

If you round this to 2dp then you get 3.16 and if our number must be less than 3.16 then only 3.15 works. But that isn't what the question says.

We have to find a number, one property of which is it's less than root 10. Then, and only then, round it to 2dp.  By that logic 3.16 fits too.

Ho hum, never mind; it's a minor point.

Bob

Don't go crazy with just one problem. It's not like I need it for an exam.

Keep_Relentless

Member

From: Queensland, Australia

Registered: 2024-05-05

Posts: 61

Re: Name the Number

Anything larger than pi and less than root 10 works.

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"The most incomprehensible thing about the world is that it is comprehensible." -Albert Einstein.

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Name the Number

Anything larger than pi and less than root 10 works.

Ok. Very good. Thanks for your input. Look for more basic probability problems later on today.