Question

The difference in elevation of a helicopter and a submarine is `18 1/2` meters. The elevation of the submarine is `-7 3/4` meters. What is the elevation of the helicopter?

Answer 1

`10 3/4`meters high

Explanation:

The negative elevation of the submarine means it is `7 3/4` meters below the surface of the water. (no surprises there!)

We know the DIFFERENCE in their elevations, so we know that the helicopter is `18 1/2` meters higher than the submarine., but how far above sea level water is it?

Add on the difference:

`-7 3/4 + 18 1/2`

This is probably easier written as `18 1/2 -7 3/4`

Work with the whole numbers then find a common denominator for the fractions.

=`11 (2-3)/4 color(white)(....................)OR = 10 (4+2-3)/4" "` "borrow" `1 = 4/4`

=`11 -1/4 color(white)(.............................)= 10 3/4` meters high

=`10 3/4` meters high

If you realise that `1/2` is less than `3/4`, you can also change to improper fractions, which avoids having to 'borrow' (convert) a whole number, but the numbers are bigger.

`18 1/2 -7 3/4`

=`37/2 -31/4`

=`(74- 31)/4`

=`43/4`

=`10 3/4`meters

Answer 2

`10 3/4" metres"`

The units of measurements are important. Gets you extra marks

Explanation:

If you are not quite sure about this question type draw a rough sketch. It only needs to be a rough sketch as there is not much time in an exam.

Let the height of the helicopter above sea level be `h`

The elevation (height) of the helicopter above sea level is:

`h =18 1/2-7 3/4 = 10 3/4" metres"`