F.1 to F.2 maths 題目一問

1)1,3,9,27 is 30,31,32,33
So general term is 3n-1
2)A,B,C have a total of 69kg rice.If A has one third of the rice of B and B has 5 times as much as C.Find the amount of rice each person has.
A+B+C = 69 … (1)
A = B/3 … (2)
B = 5C or C = B/5 … (3)
Put (2) & (3) into (1) => B/3 + B + B/5 = 69
5B/15 + 15B/15 + 3B/15 = 69
23B/15 = 69
B = 60*15/23 = 45
A = B/3 = 15
C = B/5 = 9
A,B,C have 15kg, 45kg and 9kg of rice respectively.
3)Sam and Ray share $180 pocket money in ratio of 4 : 5.How much does each boy have?
Sam has $180 * 4 / (4+5) = $80
Ray has $180 * 5/(4+5) = $100
4)C6DF place value of D
The place value is 16. The value of this digit is 16 x 13 = 208
5)101(1)101 place value of 1 in( )
The place value is 8