Cupcakes are sold in packages of 10 and 15. Jean bought 4 packs of 15 cupcakes.  If she will give one cupcake each to 100 children in the orphanage, how many packs of 10 cupcakes should she need to buy?
Jean already bought 15 cupcakes x 4 packs = <<15*4=60>>60 cupcakes.
She needs 100 - 60 = <<100-60=40>>40 more cupcakes.
Thus, she needs to buy 40/10 = <<40/10=4>>4 packs of 10 cupcakes.
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