Lee has three different coloured balls, which each have different weights and are balanced on the two scales shown below.
 
 
<img src='https://firebasestorage.googleapis.com/v0/b/prep-alpha.appspot.com/o/2018_B_Q22_1?alt=media&token=be3bc558-931b-4d27-b0ef-ae84f114db22' style="margin-top:15px;margin-bottom:15px;margin-left:15px"/>
 
 
The mass of one green ball is 12 grams.
 
 
What is the mass of a single red ball?

<img src="https://firebasestorage.googleapis.com/v0/b/prep-alpha.appspot.com/o/Irene_Y5_J1718_31?alt=media&token=b24a7c21-d454-4350-a265-d5665876ae3a" width="210" aspect-ratio="922/196" alt="image" style="margin-top:15px;margin-bottom:10px;margin-left:10px"/> 
What is <img src="https://firebasestorage.googleapis.com/v0/b/prep-alpha.appspot.com/o/2013_A_Q15_1_V6?alt=media&token=4f21edc7-4d2e-42b9-ab7c-d43b1890df9b" width="34" aspect-ratio="146/174" alt="image" style="margin-top:0px;margin-bottom:-2px;margin-left:-3px;margin-right:-3px"/> ?

Kira has a bag containing three different coloured marbles labelled purple, blue, and yellow.
 
 
<img src="https://firebasestorage.googleapis.com/v0/b/prep-alpha.appspot.com/o/Irene_Y5_O1718_12?alt=media&token=378c4dc0-dcea-4262-8e8f-00cb98a29122" width="280" aspect-ratio="1095/903" alt="image" style="margin-top:-10px;margin-bottom:15px;margin-left:-25px"/>
 
 
Kira's friend Julie takes out one purple marble and puts it to the side, leaving the rest of the marbles in the bag.
 
 
What is now the chance of Kira taking out a blue marble?

Patrick measured his height. He then stood on four blue blocks and measured his height again.
 
 
<img src='https://firebasestorage.googleapis.com/v0/b/prep-alpha.appspot.com/o/2018_B_Q32_1?alt=media&token=4d835a6a-2d3f-40aa-a172-52fe82c2a20a' style="margin-top:15px;margin-bottom:15px;margin-left:20px"/>
 
 
He then removed two of the blue blocks.
 
 
What is his height, in cm, after removing two blue blocks?

<img src="https://firebasestorage.googleapis.com/v0/b/prep-alpha.appspot.com/o/2015_B_Q39_1_v3?alt=media&token=c54508c7-642d-4259-9eb3-08127a798b50" width="450" aspect-ratio="1949/877" alt="image" style="margin-top:15px;margin-bottom:15px;margin-left:25px"/> 
Which of these statements is true? 
<img src="https://firebasestorage.googleapis.com/v0/b/prep-alpha.appspot.com/o/Y5_J1516_20v2?alt=media&token=da0dfbaf-64ae-4c2f-b63c-1ba7ac2fe7d1" width="480" aspect-ratio="2073/1110" alt="image" style="margin-top:20px;margin-bottom:20px;margin-left:15px"/>