We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive pseudonymised information about your use of our website.
Please click on "Accept cookies" if you agree to the setting of cookies. Cookies that do not require consent remain unaffected by this, see
cookie policy and privacy policy.
DECLINE COOKIES

A textbook has 1,000 pages. How many of the pages have page numbers whose digits add up to exactly 4?

Guest Jun 13, 2017

#1**+3 **

This probably isn't the "smartest" method, but I just wrote them all out here.

I noticed that they follow a kind of pattern.

004

013 103

022 112 202

031 121 211 301

040 130 220 310 400

I count fifteen of them.

hectictar Jun 13, 2017

#2**+3 **

That is a good method Hectictar, I just want to take a look too :)

400 any order 3 The 4 can be 1st , 2nd or 3rd.

310 any order 3*2=6 ways these pages are 13,31,103,130,301,310

211 any order 3

220 any order 3 ways

15 ways WE agree

Melody Jun 13, 2017

#3**+1 **

Well, you can immediately eliminate the possibility of any of the digits being 5,6,7,8, or 9 because that would result in a sum greater than 4, which simplifies the problem somewhat.

TheXSquaredFactor Jun 13, 2017