Question 785456
The ratio of (fertilizer mL) to liters of water is 40 to 8/9.
Water volume will be measured in liters, fertilizer in milliliters,
No conversions needed.
 
IF IT IS A REAL LIFE PROBLEM,
The bucket probably has some graduation lines  to roughly measure the amount of water, marking {{{1L}}}, {{{1&1/2}}}{{{L}}}, {{{1&3/4}}}{{{L}}}.
I would just double both quantities.
I would measure {{{2*(8/9)=16/9=1&7/9}}} liters of water.
That's between {{{1&3/4=1.75}}} and 1.8 liters, because
{{{2*16/9=1&7/9=1.777}}}{{{"....."}}}
and you hopefully have markings for {{{1&3/4}}}{{{L}}} or {{{1.8L}}} on the bucket.I would mix into that {{{2*40ML= 80mL}}} fertilizer.
That is 1/3 of a cup.
If you could only measure exactly 2L, ask a friendly chemist (like me) to borrow a graduate cylinder to measure 86mL of fertilizer (calculated below) and dilute that to the 2L mark with water.
 
IF IT IS A MATH CLASS PROBLEM,
you are probably expected to calculate how to make a full 2.0L of dilued fertilizer.
{{{2L(1000mL/("1 L"))=8000/9}}}{{{mL}}} of water-fertilizer mix is desired.
{{{8/9}}}{{{L}}}{{{(1000mL/("1 L"))=8000/9}}}{{{mL}}} of water
When that amount of water is mixed with {{{40mL}}} fertilizer, you get
{{{8000/9}}}{{{mL+40mL=8000/9}}}{{{mL+360/9}}}{{{mL=8360/9}}}{{{mL}}} mix
The fertilizer to final mix ratio (both volumes in mL) is
{{{40/((8360/9))}}}
(For a nathematically exact answer, we need to work with fractions.
If you are expected/allowed to approximate to a decimal, you could use 929, or 928.9, or 928.888... with up to as many digits as your calculator can handle).
 
{{{x}}} = mL of fertilizer to be mixed with water.
The proportion to find how much fertilizer to use for 2L (2000mL) of diluted fertilizer is
{{{x/2000=40/((8360/9))}}}
{{{x/2000=40(9/8360)}}}
{{{x/2000=40*9/8360)}}}
{{{x=2000*40*9/8360)}}}
Simplifying
{{{x=2000*4*9/836)}}}
{{{x=2000*9/209)}}}
{{{x=18000/209="approx."}}}{{{86mL)}}}