To call someone on a cellphone, you just tap the numbers on the screen, or maybe just their name. But even just 20 or 30 years ago, some phones still had a “rotary dial.” The spinning wheel had a hole for each digit from 0 to 9. To dial a number, you stuck your finger in each digit’s hole and spun the wheel, then let go so it could spin back and make that many clicks. For 9 and 0 you had to wait for 9 and 10 clicks. By the time the person answered, you’d forgotten why you had called!
Lace up: For which number will you hear more clicks, a 3 or a 7?
Jog: If you dial a 2, then a 4 then a 6…what digit should you dial next?
Sprint: To save everyone lots of clicks, the lowest-number area codes (the first 3 digits) were given to the cities with the most people. How many more clicks would you hear for Washington, DC (202) than for New York (212)?
Hurdle: Which area code with just one 0 in the middle would make 28 clicks?
High Jump: How many clicks would people hear if they called your number on a rotary phone today? (You can use your 10-digit home phone number, or a cell phone #.)
Pole Vault: How many different 3-digit area codes would give you a lucky 7 clicks? (Any order counts — don’t worry whether they are real-life area codes).
Answers:
Lace up: A 7 has more clicks.
Jog: 8.
Sprint: 9 more — 14 clicks for 202, but just 5 clicks for 212.
Hurdle: Just one: 909 (it needs 18 clicks beyond the 10 clicks from the 0).
High Jump: Different for everyone…add up the digits of your main phone number, but remember 10 for each 0!
Pole Vault: 15 different area codes. To start, there are 4 combinations of digits that would work: 115, 124, 133, and 223. You can’t use 0 because it gives you 10 clicks, not 0. Then each of those has either 3 or 6 combinations: there are 6 if all the digits are different, but just 3 combinations if 2 digits are the same. This gives us 15 choices:
115, 151, 511
124, 142, 214, 241, 412, 421
133, 313, 331
223, 232, 322
115, 151, 511
124, 142, 214, 241, 412, 421
133, 313, 331
223, 232, 322
