1,800
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Let's try to divide 1,772 and see how much math we need to do...
1,772 / 90 = 19.6888888889
Well, clearly we need more than 1,772! 
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Now, play around with adding numbers.
(I'm gonna skip all the experimenting, here's the closest # available for easy division!)
⇣
1,800 / 90 = 20