Posted by joi on Tuesday, December 27, 2011 at 11:22am.
1. Three boxes A, B and C weigh 12kg altogether. Box A weighs 1.2kg more than B and 0.3kg more than C. What is the weight of the heaviest box?
2. Peter and Ali have 375 cards altogether. If Ali gives 25% of his cards to Peter, he will have 1/4 as many cards as Peter. How many cards does Ali have?

maths p5  Steve, Tuesday, December 27, 2011 at 3:40pm
1)
A = B + 1.2
A = C + .3
so,
C = B + .9
so,
A+B+C = B+1.2 + B + B+.9 = 12.0
3B + 2.1 = 12.0
B = 3.3
A = 4.5
C = 4.2
2)
If p a gives 1/4 of his cards to p,
3/4 a = 1/4(p + a/4)
3a = p + a/4
12a = 4p + a
11a = 4p
so,
a + p = a + 11/4 a = 375
15a/4 = 375
15a = 1500
a = 100
so, p = 275
if a gives 25 to p,
then a = 75 and p = 300