Answer :
610-187 is 423 but when you estimate it would be 400 this is your answer
⇒We have to estimate the difference
=610 - 187
Actual Estimation= 423
⇒Estimation using Tens
=610 - 190
= 420
⇒Estimation using Hundreds
=600 - 200
= 400
→Correct estimation is
Estimation using Tens=420
