estimation for hundred thousands: 500,000 + 300,000 = 800,000
estimation for ten thousands: 460,000+260,000 = 720,000
estimation for thousands: 463,000 + 257,000 = 720,000
estimation for hundreds: 462,800 + 256,700 = 719,500
estimation for tens: 462,810 + 256,740 = 719,550
estimation for ones: 462,809+256,738 = 719547
hope this helps