If a kilometer is equal to .621 miles, how many kilometers is one mile equal to?

2 Answers
smendyka
Oct 22, 2017

See a solution process below"

Explanation:

We can write this relationship as:

#1"km" = 0.621"mi"#

We can now divide each side of the equation by #color(red)(0.621)# to solve for #1"mi"# while keeping the equation balanced:

#(1"km")/color(red)(0.621) = (0.621"mi")/color(red)(0.621)#

#1.610"km" = (color(red)(cancel(color(black)(0.621)))"mi")/cancel(color(red)(0.621))#

#1.610"km" = 1"mi"#

one mile is about 1.610 kilometers

Tony B
Oct 22, 2017

The count of kilometres in 1 mile is #1.610# to 3 decimal places

Explanation:

Let the unknown count of kilometres be #x#

Use ratio in fraction format.
We need kilometres so put them at the top (numerator position)

# ("kilometres")/("miles") -> 1/0.621 =x/1#

#color(brown)("This is where the shortcut comes from:")##color(brown)("If we change the 0.621 int0 1 and do the same to"##color(brown)("the top we will have our answer")#

#x/1 = (color(green)(1-:0.621))/(0.621-:0.621) = (1.610305.....)/1#

The question uses 3 decimal places so we need to do the same:

#1.610# to 3 decimal places

#color(brown)("Shortcut")#
Just divide the bottom into the top #color(green)(1-:0.621)#

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