You have to do regrouping and borrowing

来源: elfie 于 2021-09-24 17:46:50 [] [旧帖] [给我悄悄话] 本文已被阅读： 次 (144 bytes)

It takes more mental work to do subtraction. You don't need to do any calculation to know 7+3=10. 2+3=5. It's just intuitive.

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• Nope, subtraction is definitely less accurate and takes more tim -elfie- ♀ 给 elfie 发送悄悄话 (174 bytes) () 09/24/2021 postreply 19:06:14

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