Difference between revisions of "1987 AHSME Problems/Problem 3"
(Created page with "==Problem== How many primes less than <math>100</math> have <math>7</math> as the ones digit? (Assume the usual base ten representation) <math>\text{(A)} \ 4 \qquad \text{(B)...") |
Slackroadia (talk | contribs) (→Problem) |
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\text{(D)} \ 7 \qquad | \text{(D)} \ 7 \qquad | ||
\text{(E)} \ 8 </math> | \text{(E)} \ 8 </math> | ||
| + | |||
| + | ==Solution== | ||
| + | |||
| + | 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 == | ||
Revision as of 17:40, 23 April 2017
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. 
