Grade 4

Add it without adding

Three sums that look like work and are not -- pair the ends, balance the scale, or let the subtractions fold together.

1
Nine in a row
Find the sum. $21 + 22 + 23 + \dots + 27 + 28 + 29$
2
Balance the scale
Which number makes the equation true? $215 + \square = 318 + 245$
3
Two cuts
Find the value of $x$ . $789 - x - 251 = 302$