Estimation
Find the about answer:
23+45=?
20+50=70
24+32=?
56
75-23=?
52
Mary cooks 56 cookies. 36 of them are chocolate chip and 20 of them are sugar. She gives away 31 cookies to her friend Bill. How many does she have left?
25 cookies
Mentally subtract 2:
15, 25, 35, 45
13, 23, 33, 43
Find the about answer:
67-34=?
70-30=40
33+66=?
99
86-43=?
43
Joe takes 34 pictures. Then he takes 17 more. He decides he does not like 6 of them so he throws them away. How many pictures does he have?
45 pictures
Solve:
25+10-15=?
20
Find the about answer:
93-25=?
90-30=60
75+37=?
112
63-47=?
16
Karen makes gift bags for her birthday party. she puts 5 pieces of candy in each bag. How many pieces of candy does she need to make 11 gift bags?
55 pieces
7 tens 13 ones
Find the about answer:
85+15=?
90+20=110
146+35=?
181
71-48=?
23
Susan has 58 blue stones for her project. Ross has 15 more blue stones than Susan. Ross also has 20 purple stones. How many stones does Ross have all together?
93 stones
Solve:
13+30-3=?
40
Find the about answer:
12+75=?
10+80=90
273+127=?
400
124-85=?
39
Gia paints shells as gifts. She puts 7 starfish stickers on each shell. How many stickers does she need to make 8 shells?
56 stickers
Solve:
96-30+4=?
70