Difference between revisions of "1987 AHSME Problems/Problem 3"
Slackroadia (talk | contribs) (→Problem) |
m (Fixed a punctuation error) |
||
| Line 11: | Line 11: | ||
==Solution== | ==Solution== | ||
| − | List out all numbers that have 7 as the ones digit less than 100 | + | List out all numbers that have 7 as the ones digit less than 100: <math>{7, 17, 27, 37, 47, 57, 67, 77, 87, 97}</math>. Only <math>7, 17,37, 47,67,</math> and <math>97</math> are prime. Thus, it is <math>\boxed{C}</math>. -slackroadia |
== See also == | == See also == | ||
Latest revision as of 11:18, 1 March 2018
Problem
How many primes less than 
have 
as the ones digit? (Assume the usual base ten representation)
Solution
List out all numbers that have 7 as the ones digit less than 100: 
. Only 
and 
are prime. Thus, it is 
. -slackroadia
See also
| 1987 AHSME (Problems • Answer Key • Resources) | ||
| Preceded by Problem 2 |
Followed by Problem 4 | |
| 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 • 26 • 27 • 28 • 29 • 30 | ||
| All AHSME Problems and Solutions | ||
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. 
