Singapore Primary Math Explained sc-math

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Updated: 5 November, 2007

3 |

7 |

a) What fraction of the chairs were stacked up?

b) How many chairs were arranged in rows?

(5 marks)

a)

Fraction of chairs in rows →

3 |

7 |

1 |

2 |

13 |

14 |

Therefore fraction of chairs stacked up is

1 |

14 |

b)

7 long rows → 7 short rows + 7 × 16 chairs

6 |

14 |

1 |

14 |

14 short rows → 112 chairs

each short row → 112 ÷ 14 = 8 chairs

1 |

14 |

13 |

14 |

312 chairs were arranged in rows.

Peter saved some $1 coins in the months of May and June. His mother gave him $0.50 for each $1 coin saved in the month of May. Including his mother's contribution, Peter saved a total of $195 in May and June. This was 30% more than his usual savings. How much did Peter save in June?

(4 marks)

(4 marks)

130% of usual savings → $195

100% of usual savings → $195 ×

= $150

mother's contribution → $195 − $150 = $45

mother's contribution → 50% of Peter's savings in May

Peter's savings in May → $45 ×

= $90

total savings in May → $90 + $45 = $135

savings in June → $190 - $135 = $60

Peter saved $60 in June

100% of usual savings → $195 ×

100 |

130 |

mother's contribution → $195 − $150 = $45

mother's contribution → 50% of Peter's savings in May

Peter's savings in May → $45 ×

100 |

50 |

total savings in May → $90 + $45 = $135

savings in June → $190 - $135 = $60

Peter saved $60 in June

Karen, Lena and May shared some stickers in the ratio of 3:1:4. After May gave 40% of her stickers to Karen and Lena, Karen had 90 more stickers than May and the number of Lena's stickers increased by 70%.

a) What was the percentage increase for Karen?

b) How many stickers did May have at first?

(5 marks)

a) What was the percentage increase for Karen?

b) How many stickers did May have at first?

(5 marks)

May : Karen : Lena → 4 : 3 : 1 → 100% : 75% : 25%

a)

22.5 |

75 |

Karen's percentage increase is 30%

b)

37.5% → 90 stickers

100% → 90 ×

100 |

37.5 |

Mary had 240 stickers at first

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