The weight of a small box, two medium boxes and a large box altogether is 10 kg. The weight of a small box, two medium boxes and two large boxes altogether is 15 kg. What is the total weight of two small boxes and four medium boxes?

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Answers

2014-06-01T16:49:28+05:30
Let weight of small box be (s) kg, medium box be (m) kg and large box be (l) kg
then,
1 small box + 2 medium boxes + 1 large box = 10 kg
1 s + 2 m + 1 l = 10.............(i)
                                                 AND
1 small box + 2 medium box + 2 large box = 15 kg
1 s + 2 m + 2 l = 15.............(ii)
SUBSTRACTING EQUATION (i) FROM (ii).
WE GET,
1 l = 5 kg
Therefore, weight of large box = 5 kg.
FIND:   2 small box +  4 medium box 
          2 s + 4 m = ?
1 s + 2 m + 1 l = 10                                                      [FROM EQUATION (i)]
1 s + 2 m + 5 = 10                                                       [SINCE 1 l = 5 ]
1 s + 2 m = 10 - 5
1 s + 2 m = 5...................(iii)
MULTIPLYING EQUATION (iii) BY '2' ON BOTH SIDES.
WE GET,
2 s + 4 m = 10kg
THEREFORE, WEIGHT OF 2 SMALL BOXES AND 4 MEDIUM BOXES = 10 kg
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