Using a Calculator

Converting before entering

• Quantities that are not decimal must be converted before they are typed in
• Time is the usual case, because minutes are sixtieths rather than hundredths
  • 2 hours 30 minutes is entered as 2.5 hours
  • 3 hours 20 minutes is entered as 3 ⅓ hours, since 20 minutes is a third of an hour
• Many calculators also accept a degrees-minutes-seconds key, which allows hours and minutes to be entered directly

Using brackets

• Brackets are needed wherever the written layout does its own grouping
• A fraction line groups the whole numerator and the whole denominator, and a root sign groups everything beneath it
  • (7 + 5) ÷ (9 − 3) must be typed with both brackets, or the calculator applies the division to 5 alone
• Negative numbers being squared need brackets, since without them the calculator squares first and applies the sign afterwards

Keys that save time

• The Ans key holds the previous result, so a calculation in stages continues without the last figure being retyped, and therefore without it being rounded
• The memory keys hold a value for use much later in the same question, which is what keeps full accuracy through a long chain of working
• The table function evaluates one expression at a whole list of x values at once, which fills in a table of values for a graph far faster than entering each substitution separately
• The π key keeps an answer exact for as long as it is wanted, so a result asked for in terms of π is never turned into a decimal by accident