Last Sunday, the ratio of the number of lorries to the number of cars to the number of motorcycles on the road was 11 : 5 : 20. On Monday, the number of lorries on the road remained the same. However, the number of cars increased by 50% and the number of motorcycles decreased by 10%. Find the ratio of the number of cars to the number of lorries to the number of motorcycles on the road on Monday. Express your answer in its simplest form. Ans: ___

1. Identify the initial units for each vehicle type.

Let the initial number of lorries, cars, and motorcycles be $11u$, $5u$, and $20u$ respectively.

2. Calculate the new number of units for cars.

New number of cars = $5u \times (1 + 0.50) = 5u \times 1.5 = 7.5u$

3. Calculate the new number of units for motorcycles.

New number of motorcycles = $20u \times (1 - 0.10) = 20u \times 0.9 = 18u$

4. Form the new ratio and simplify it.

New ratio of cars : lorries : motorcycles = $7.5u : 11u : 18u$
Multiply by 2 to remove the decimal:
$15 : 22 : 36$