Being 2/3 of her brother's height, Mary is 180 * 2/3 = <<180*2/3=120>>120 cm.

To reach the minimum height and ride Kingda Ka, Mery needs to grow 140 - 120 = <<140-120=20>>20 cm.

# Answer

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Mary wants to ride the world's tallest roller coaster, Kingda Ka. The minimum height to ride the roller coaster is 140 cm. Mary's brother is 180 cm, Mary is 2/3 the height of her brother. How many more centimeters does Mary need to grow to ride Kingda Ka?
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Mary wants to ride the world's tallest roller coaster, Kingda Ka. The minimum height to ride the roller coaster is 140 cm. Mary's brother is 180 cm, Mary is 2/3 the height of her brother. How many more centimeters does Mary need to grow to ride Kingda Ka?
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