PSLE
Barbara and Betty 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 39 sandwiches and had 290 g of dough left. Betty made 19 sandwiches and had 1.09 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 Betty
= 39 - 19
= 20

1 kg = 1000 g
1.09 kg = 1.09 x 1000 = 1090 g

Difference between the remaining dough left by Betty and Barbara
= 1090 - 290
= 800 g

Mass of 20 sandwiches = 800 g

Mass of 1 sandwich
= 800 ÷ 20
= 40 g

(b)
Total remaining dough left
= 1090 + 290
= 1380 g

Sets of 40 g
= 1380 ÷ 40
= 34 r 20

Number of sandwiches = 34

Answer(s): (a) 40 g; (b) 34