There are 4 tens in 640 or 640/10 = 64
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The place value of 4 is TENS and so its value is 4 lots of ten or forty.
640 grams = 22.57ounces.
There are 640 acres in a section.
640 ounces = 40 pounds
How many tens are there in 1700?
640 acres = 27,878,400ft²
640/4 = 160