Q&A - P5 Math
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Pls help me to solve last two pb sums. Tia
1) A frog is at the bottom of a well which is 31m deep. It climbs 6m up in the day and slides 4m down at night. How many days does it take for a frog to get out of the well?
2) Nathan withdrew 80% of his savings to purchase a laptop. If he were given a 15% discount on the cost price of the laptop, he could have put $390 back into his savings account. A) How much did he pay for the laptop? B) How much did Nathan have in his savings account at first? -
concerned1970:
hi, offering my help :Pls help me to solve last two pb sums. Tia
1) A frog is at the bottom of a well which is 31m deep. It climbs 6m up in the day and slides 4m down at night. How many days does it take for a frog to get out of the well?
2) Nathan withdrew 80% of his savings to purchase a laptop. If he were given a 15% discount on the cost price of the laptop, he could have put $390 back into his savings account. A) How much did he pay for the laptop? B) How much did Nathan have in his savings account at first?
Q1
It climbs 6m up in the day and slides 4m down at night
6m - 4m = 2m (means each day, the frog climbs 2m)
31m - 6m = 25m (we take it that from the last day if the frog climbs from where it was, it should be from anywhere from the 25m onwards and it would jump out of the well)
25m / 2m = 12.5 ~ 13 days.
13 x 2m = 26m
26m + 6m = 32m (out of the well.
so 13 days + 1 day = 14 days (Ans)
Q2
If he were given a 15% discount on the cost price of the laptop, he could have put $390 back into his savings account.
15% --> $390
1% --> $26
100% --> $2600 (Ans for (a))
80% of savings --> $2600
10% of savings --> $325
100% of savings --> $3250 (Ans for (b)) -
verykiasumummy:
Tysm for yr help.
hi, offering my help :concerned1970:
Pls help me to solve last two pb sums. Tia
1) A frog is at the bottom of a well which is 31m deep. It climbs 6m up in the day and slides 4m down at night. How many days does it take for a frog to get out of the well?
2) Nathan withdrew 80% of his savings to purchase a laptop. If he were given a 15% discount on the cost price of the laptop, he could have put $390 back into his savings account. A) How much did he pay for the laptop? B) How much did Nathan have in his savings account at first?
Q1
It climbs 6m up in the day and slides 4m down at night
6m - 4m = 2m (means each day, the frog climbs 2m)
31m - 6m = 25m (we take it that from the last day if the frog climbs from where it was, it should be from anywhere from the 25m onwards and it would jump out of the well)
25m / 2m = 12.5 ~ 13 days.
13 x 2m = 26m
26m + 6m = 32m (out of the well.
so 13 days + 1 day = 14 days (Ans)
Q2
If he were given a 15% discount on the cost price of the laptop, he could have put $390 back into his savings account.
15% --> $390
1% --> $26
100% --> $2600 (Ans for (a))
80% of savings --> $2600
10% of savings --> $325
100% of savings --> $3250 (Ans for (b))
But for ques 1 which u have answered, the correct ans shown is 32 days.
-
concerned1970:
Tysm for yr help.
hi, offering my help :verykiasumummy:
[quote=\"concerned1970\"]Pls help me to solve last two pb sums. Tia
1) A frog is at the bottom of a well which is 31m deep. It climbs 6m up in the day and slides 4m down at night. How many days does it take for a frog to get out of the well?
2) Nathan withdrew 80% of his savings to purchase a laptop. If he were given a 15% discount on the cost price of the laptop, he could have put $390 back into his savings account. A) How much did he pay for the laptop? B) How much did Nathan have in his savings account at first?
Q1
It climbs 6m up in the day and slides 4m down at night
6m - 4m = 2m (means each day, the frog climbs 2m)
31m - 6m = 25m (we take it that from the last day if the frog climbs from where it was, it should be from anywhere from the 25m onwards and it would jump out of the well)
25m / 2m = 12.5 ~ 13 days.
13 x 2m = 26m
26m + 6m = 32m (out of the well.
so 13 days + 1 day = 14 days (Ans)
Q2
If he were given a 15% discount on the cost price of the laptop, he could have put $390 back into his savings account.
15% --> $390
1% --> $26
100% --> $2600 (Ans for (a))
80% of savings --> $2600
10% of savings --> $325
100% of savings --> $3250 (Ans for (b)) But for ques 1 which u have answered, the correct ans shown is 32 days.[/quote]to calculate on daily basis for Q1 :
day 1 : + 6m, - 4m = 2m
day 2 : 2m + 6m - 4m = 4m
day 3 : 4m + 6m - 4m = 6m
day 4 : 6m + 6m - 4m = 8m
day 5 : 8m + 6m - 4m = 10m
day 6 : 10m + 6m - 4m = 12m
day 7 : 12m + 6m - 4m = 14m
day 8 : 14m + 6m - 4m = 16m
day 9 : 16m + 6m - 4m = 18m
day 10 : 18m + 6m - 4m = 20m
day 11 : 20m + 6m - 4m = 22m
day 12 : 22m + 6m - 4m = 24m
day 13 : 24m + 6m - 4m = 26m
day 14 : 26m + 6m = 32m (already out of well)
the ans is still 14 days... is your ans sheet wrong? -
Ty verykiasumummy and quekcc. I don’t know, verykiaumummy. It’s CHIJ SA2 paper 2009 I suppose. No working is shown only ans provided.
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concerned1970:
Ty verykiasumummy and quekcc. I don't know, verykiaumummy. It's CHIJ SA2 paper 2009 I suppose. No working is shown only ans provided.
i would say the ans is wrong... there is no way to get 32 days at all.... -
hi all,
2011-MGS-SA2-Paper2
Qn17
M, N, O shared the cost of rental flat. M paid 2/5 of the total amount paid by N and O. The ratio of the amount paid by N to the total amount paid by M and O is 1:3.
(a) what is the ratio of the rent paid by M to N to O? (8:7:13)
(b) given that M paid $35 more than N, how much rent did the 3 girls pay for the flat? (Ans:$980)
thank you -
shawnlim88:
hi, offering my help :hi all,
2011-MGS-SA2-Paper2
Qn17
M, N, O shared the cost of rental flat. M paid 2/5 of the total amount paid by N and O. The ratio of the amount paid by N to the total amount paid by M and O is 1:3.
(a) what is the ratio of the rent paid by M to N to O? (8:7:13)
(b) given that M paid $35 more than N, how much rent did the 3 girls pay for the flat? (Ans:$980)
thank you
M paid 2/5 of the total amount paid by N and O.
M : N + O
2 : 5 ------ x 4
The ratio of the amount paid by N to the total amount paid by M and O is 1:3
N : M + O
1 : 3 ------- x 7
both ratios are constant total. (1st ratio x 4, 2nd ratio x 7)
therefore :
M : N + O
8 : 20
N : M + O
7 : 21
M : N : O
8 : 7 : 13 (ans for a)
M : 8u
N : 7u
8u - 7u = 1u
1u --> $35
8u + 7u + 13u = 28u
28u --> $980 (ans for b) -
this question is taken from Nanchiau P5 SA2 2012.
Can somebody help to answer ? thanks
Wendy had 2 bags of rice, A and B, weighing 88 kg altogether.
The bags contained different amount of rice. Wendy poured 1/3 of the rice from bag A to bag B. Then she poured 1/5 of the rice from bag B bag A, As a result, both bags had the same
How much rice was there in bag A at first? -
zombie:
working backwards method :this question is taken from Nanchiau P5 SA2 2012.
Can somebody help to answer ? thanks
Wendy had 2 bags of rice, A and B, weighing 88 kg altogether.
The bags contained different amount of rice. Wendy poured 1/3 of the rice from bag A to bag B. Then she poured 1/5 of the rice from bag B bag A, As a result, both bags had the same
How much rice was there in bag A at first?
88 / 2 = 44kg (weight in the end)
in B :
1 - 1/5 (to A) = 4/5
4/5 --> 44kg
1/5 --> 11kg
5/5 --> 55kg (weight of B after 1/3 of A is transferred to B)
88 - 55 = 33kg (weight of A after 1/3 transferred to B)
2/3 of A --> 33kg
1/3 of A --> 16.5kg
3/3 of A --> 49.5kg (A at first)
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