Home Models & Strategies · Grade 4 Rounding & Estimating: Six Ways One problem, 4,367 + 2,258 = 6,625, estimated six ways, and the same moves work for × and ÷. the same number rounds UP to one place and DOWN to another to the nearest hundredto the nearest thousand 4,4004,300 4,350 · halfway 4,367 past halfway → 4,400 5,0004,000 4,500 · halfway 4,367 not yet halfway → 4,000 Vertical number line Read this one the midpoint decides, and a number sitting exactly on it always rounds UP not yet at the midpointexactly on the midpoint 4,0005,000 4,500 4,367 4,367 has not reached 4,500, so it is nearer 4,000 4,367 ≈ 4,000 4,0005,000 4,500 4,500 4,500 sits exactly on the midpoint: round UP 4,500 ≈ 5,000 the same rule at any place: 250 ≈ 300, 4,350 ≈ 4,400 The halfway mark Read this one look at the digit to the RIGHT of the place you want nearest hundred 4,367 the 6 in the tens place → 5 or more, round UP ≈ 4,400 nearest thousand the 3 in the hundreds place → less than 5, round DOWN 4,367 ≈ 4,000 The digit rule · the shortcut Read this one round to the hundred, then do the easy problem 4,3672,258 →→ 4,4002,300 + 6,700 round to the thousand instead and you get 4,000 + 2,000 = 6,000: a wider net 4,367 + 2,258 ≈ 6,700 Round both, then compute Read this one swap in numbers that are friendly together: this works for all four operations addingmultiplying and dividing 4,3672,258 →→ 4,4002,300 + 6,700 hundreds are friendly to add 24 × 6→25 × 6 144 ÷ 6→150 ÷ 6 ≈ 150≈ 25 friendly with 6 · exact answers 144 and 24 Compatible numbers Read this one the estimate is how you catch a wrong answer my estimate ≈ 6,700 my exact answer 6,625 vs close: the answer makes sense ✓ but if you ignored the thousands and got 625 … 625 is ten times too small: go back and check an estimate does not give the answer; it guards it Is it reasonable? Read this one