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1. A box of thumbtacks weighed 1,590 grams. The box of thumbtacks weighed 1,470 grams after 40 thumbtacks were taken out from the box. How many thumbtacks were there in the box at first?  


2. A big box can hold 12 marbles and a small box can hold 5 marbles. There are a total of 99 marbles. How many big boxes are there?

 Apr 9, 2021
 #1
avatar+31826 
+2

Find per unit wt of tack

(1590 - 1470) / 40    gm / tack

 

Now divide starting wt / unit weight to find tacks

 

1590 gm /  [(1590 - 1470) / 40] gm/tack     = 530 tacks

 Apr 9, 2021
 #2
avatar+31826 
+2

Here is one way   start at 99 and count backwards by 5's until you hit a multiple of 12

   99 - 5 = 94

         94 - 5 = 89

             89 - 5 = 84    Bingo !     84/12 = 7 large boxes     and 3 small boxes

 

But wait....     what about 24 ?     then there would be 2 large boxes    and  15 small boxes

 Apr 9, 2021

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