Question

add/subtract medium difficulty
part 1 of 2 1 2 trying to earn:
do these problems in your head. use paper only for the problems that you just cant do in your head. its importan
do as many of these problems without paper as you can.
do not use a calculator at all.
72 + 7 =
620 + 20 =
20 + 15 =
41,000 + 5,000 =
5000 + 2100 =
0.4 + 9.4 =
1.2 + 4.0 =
0.81 + 0.08 =
0.23 + 0.3 =

Explanation:

Step1: Add whole numbers (tens/ones)

$72 + 7 = 79$

Step2: Add whole numbers (hundreds/tens)

$620 + 20 = 640$

Step3: Add small whole numbers

$20 + 15 = 35$

Step4: Add large whole numbers

$41,000 + 5,000 = 46,000$

Step5: Add whole numbers (thousands/hundreds)

$5000 + 2100 = 7100$

Step6: Add decimal numbers

$0.4 + 9.4 = 9.8$

Step7: Add decimal/whole number

$1.2 + 4.0 = 5.2$

Step8: Add two small decimals

$0.81 + 0.08 = 0.89$

Step9: Add decimals (different places)

$0.23 + 0.3 = 0.53$

Answer:

79
640
35
46,000
7100
9.8
5.2
0.89
0.53