PSLE
Barbara and Xuan each had a plate of dough of the same mass for making sandwiches. The same mass of dough was used for each sandwich. Barbara made 30 sandwiches and had 500 g of dough left. Xuan made 12 sandwiches and had 1.31 kg of dough left.

1. What was the mass of dough needed for each sandwich?
2. With the remaining dough from both girls, how many more such sandwiches can be made at most? 

(a)
Difference between the number of sandwiches made by Barbara and Xuan
= 30 - 12
= 18

1 kg = 1000 g
1.31 kg = 1.31 x 1000 = 1310 g

Difference between the remaining dough left by Xuan and Barbara
= 1310 - 500
= 810 g

Mass of 18 sandwiches = 810 g

Mass of 1 sandwich
= 810 ÷ 18
= 45 g

(b)
Total remaining dough left
= 1310 + 500
= 1810 g

Sets of 45 g
= 1810 ÷ 45
= 40 r 10

Number of sandwiches = 40

Answer(s): (a) 45 g; (b) 40