Please explain the ticked one
Please explain as fast as possible
Please :-(
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it is talking about estimation property so for example 33 x 45 so we will round off like 33 to 30 and 45 to 50 and then multiply 30 and 50 = 1500 so coming on your problem 
1938 x 99 =
2000 x 100 = 
200000 -ans 
1938 to thousands and 99 to hundreds