In a neighborhood, there are several houses with doorplate numbers that are all odd. The first doorplate number is 123 and the last one is 273. How many houses are there?
Answer Choices
Correct answer marked belowSee the full step-by-step explanation
You can see the correct answer above. Sign in for free to unlock the complete worked solution.
Track your performance and improve
Get detailed analytics, unlock full explanations, and move up difficulty tiers as you practice.
Official Explanation
Read the full explanation
Sign in for free to see the complete step-by-step solution to this question.
Great!
pls explain more?
wait why isn't it just 273-123? I got a number close to one of the choices and now I'm second guessing myself lol
because both ends count too, not just the gap between them. think of it like counting odd numbers in a list
and don't forget it's only the odd ones, so you can't count every integer in between
quick one, felt good to get it right on the first try. counting terms of an arithmetic sequence, standard stuff
the answer choices here are a giveaway, only one is small enough to make sense. nice easy one to warm up
What it tests
Your ability to spot and extend arithmetic and geometric sequences and work with recursive definitions.
Common trap
Off-by-one errors in indexing (a₀ vs a₁) or confusing an arithmetic difference with a geometric ratio.