Thursday, October 7, 2010

Whole Number PSLE 2010 P2 Q11

Sam packed 320 marbles into four boxes, labelled A, B, C and D. Box A had the most number of marbles and box D had the least. The difference in the number of marbles between Box A and the number of marbles in the other three boxes were 8, 13 and 19.
How many marbles were there in Box D?

D []<----- 19 ----->    ]
C [][ 6 ]<-- 13 --->    ]
B [][ 11  ]<-- 8 -->    ] 320
A [][        19        ]   ]

4 u  -->  320  - 6 - 11 - 19 = 284    Small unit -- D

1 u --> 284 / 4 = 71

It is 71 marbles.


Alternative method (model drawing is actually not required)
------------------------
A [                             ]      ]
B [                 ]<-- 8-->      ]
C [             ]<-- 13 --->     ]  320
D [     ]<---- 19 -------->     ]


4 u  -->  320  +  8  +  13  +  19  =  360     Big units -- A 

1 u -->  360 / 4  =  90

90  -  19  =  71

It is  71  marbles.

2 comments:

  1. As appeared in PSLE 2010 exam:

    Sam packed 320 marbles into four boxes, labelled A, B, C and D. Box A had the most number of marbles and box D had the least. The difference in the number of marbles between Box A and the number of marbles in the other three boxes were 8, 13 and 19.
    How many marbles were there in Box D?

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