Computation Race 1

Let's have a race between brains and calculators. If you are using a calculator, you must find answers to all the problems with a calculator. If you're using your brain, you are welcome to use paper.

1.
1
+5
 2.
2
+8
 3.
4
+6
4.
9
+1
 5.
1
+9
 6.
30
+70
7.
70
+30
 8.
400
+600
 9.
500
+500
10.
800
+200
 11.
7
–2
 12.
70
–20
13.
6
–0
 14.
6
–1
 15.
60
–10