Calculate Monday Grey balloons

Given the ratio P:G=3:4 and P:Gr=3:2, the combined ratio is P:G:Gr = 3:4:2. Total parts = $3+4+2=9$. Grey balloons = $\frac{2}{9} \times 450$.

$\text{Grey}_{\text{Mon}} = \frac{2}{9} \times 450 = 100$

Calculate Tuesday Grey balloons

Given G:Gr = 9:8, let G=$9x$ and Gr=$8x$. Then P = $1.375 \times 8x = 11x$. Given P = G+40, so $11x = 9x + 40$, which gives $2x=40$ or $x=20$. Grey balloons = $8 \times 20$.

$\text{Grey}_{\text{Tue}} = 8 \times 20 = 160$

Calculate Wednesday Grey balloons

The problem directly states that the number of grey colour balloons manufactured on Wednesday is 240.

$\text{Grey}_{\text{Wed}} = 240$

Calculate average

Sum the grey balloons for the three days and divide by 3: $(100 + 160 + 240) / 3 = 500 / 3$.

$\text{Average} = \frac{100 + 160 + 240}{3} = \frac{500}{3} \approx 166.67 \approx 167$