What is the square root of 239,121?
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This one looks scary but it's actually quick if you use the last digit trick. Numbers ending in 1, so the root must end in 1 or 9. Only one answer choice does that. Nice time saver.
Yep, that's exactly how I did it. Took like 10 seconds.
Wait, does the last digit trick always work? Or just when the square ends in specific digits?
Got 497 after testing, but I wasted a minute doing 500^2 and working backwards. Anyone have a cleaner mental math approach for these?
500^2 = 250000, so root is a bit less than 500. Then check the units digit and you're down to one choice.
Medium difficulty for me. I knew the 500^2 anchor but still had to double check between 489 and 497. The answer choices are close enough to make you think.
Thanks, this reminded me I need to memorize squares up to 30 at least. The 490^2 vs 500^2 range tripped me up initially.
What it tests
Your handling of square and higher roots, including simplifying radicals.
Common trap
Forgetting the ± when taking a square root to solve an equation, or assuming √(a²) = a.