Calculator patterns

This task is about finding rules for number patterns made on a calculator.

illustration: calculator

Talia was using a calculator to make number patterns. If you keep pressing the equals button from a calculator button
on Talia's calculator it keeps making the same change to the number.

Fill in the boxes with a number. Fill in the circles with an operation sign (+, ×, ÷, or –). An example has been done for you.
 
 
                         Pattern: 2, 9, 16, 23, 30 …

Talia pressed     2 button          plus         7 button          equals button

 

a)

 
Pattern: 4, 20, 100, 500, 2500 …

Talia pressed     4 button          blank circle          blank square          equals button
 

b)

Pattern: 70, 62, 54, 46, 38 …

Taila pressed     7 button          nought button          blank cicrle          blank square          equals button
 

c)

Pattern: 45, 36, 27, 18, 9 …

Taila pressed     4 button          5 button           blank circle          blank square          equals button
 

d)

Pattern: 80, 40, 20, 10, 5 …

Taila pressed     8 button          nought          blank circle          blank square          equals button